Smasher cards are the main force you use to fight your opponent with. Smasher cards come in a large variety and can all have their own unique abilities. There are 5 different kinds of Smashers; Basic Smashers, Evolved Smashers, Smasher Ex, Smasher FS, and Smasher SP.
Basic Smashers
Basic Smashers can be played straight from your hand and do not need to played over on top of other cards. This makes Basic Smashers the easiest kinds of Smashers to play but are generally the weakest.
Name: Name of the card.
Stage: Displays the level of evolution.
Smasher Type: The Energy type assigned to the Smasher. This determines what types of Smasher this Smasher's attacks will be strong and weak against.
Hit Points: How much damage this Smasher can take before they are Knocked Out.
Smash Power/Body: Displays the effect of a Smash Power/Body. Most Smash Powers can be activated at any time (even while that Smasher is on your Bench), but some have restrictions on when they can be activated. A Smasher can also use a Smash Power and attack on the same turn. Smash Bodies are passive effect that are either always active or are triggered by an effect.
Attack Cost: Shows the Energy types required to be attached to the Smasher in order to use the attack. Any type of Energy cards can be used to fulfill the requirements of 
symbols. Attacks with a 
do not need any Energy in order to perform the attack. (That type of symbol is usually only found on attacks from Support cards.)
Attack Text: Displays any effects of the attack.
Attack Damage: Shows how much damage the attack deals. (Sometimes the damage number will be in the Attack Text.) Every 10 damage is equal to 1 damage counter.
Weakness: Displays the Energy type of Smashers that this Smasher will take extra damage from.
Resistance: Displays the Energy type of Smashers that this Smasher will take less damage from.
Retreat Cost: Displays how much Energy attached to this Smasher is needed to be discarded in order to retreat that Smasher back to your Bench. Only the Active Smasher can retreat.
Set Symbol: Displays the symbol of the set this card belongs to.
Rarity Symbol: Determines how rare the card is.
Collector Card Number: Shows what number the card is in its set. This makes it easier to identify specific cards in a set that can have cards with the same name.
Evolved Smashers
Evolved Smashers are stronger Smashers with more HP and have stronger attacks. However, they require another Smasher to be in play to be put on top of that Smasher. So if you don't have the right Smasher card in play, you can't play that Evolved Smasher. This makes them more difficult to play compared to Basic Smashers.
This is a Stage 1 Smasher that you put on top of one of your Basic Smashers. Under the name of the Smasher is the details about which card this Smasher can be put on top of. For example, Giant Donkey Kong may only be put on top of a Smasher with the name Donkey Kong. (The picture in the top left of the card helps identify this Smasher.)
When you evolve a Smasher, all cards attached to the previous Smasher stay on the new Evolved Smasher. All damage counters on the previous Smasher are put onto the Evolved Smasher. However, all Special Conditions that the previous Smasher was affected by are not put onto the Evolved Smasher, curing that Smasher of those Conditions. This includes additional effects that the previous Smasher was affected by.
You can also evolve a Stage 1 Smasher into a Stage 2 Smasher. Which are even stronger than Stage 1 Smashers but are more difficult to play because they have the same rules of playing them as Stage 1 Smashers do.
Smasher Ex
Ex Smashers are far more powerful than your average Smashers, containing more HP and stronger attacks. Below is an example of an Ex Smasher.
http://www.crimson-castle.co.uk/supersmashcards/sets/cards/smashbros/SSB01MasterHandR12.png
Compared to other Smashers, Master Hand has very high HP, his attack can target any of your opponent's Smashers, and Creator allows you search for any Smasher (excluding Ex and FS Smashers) in your deck to send to your hand.
However, Ex Smashers do have their disadvantages. If your opponent manages to Knock Out any of your Ex Smashers, they get a take 2 Prize cards instead of 1 (or draw 2 cards in non-Prize matches). You can also only have 1 copy of each Ex Smasher, which counts to the same name total as their non-Ex variants (e.g you can have 3 Mario and 1 Mario Ex but not 4 Mario and 1 Mario Ex).
Smasher FS
FS Smashers contain unique abilities and attacks that can be far stronger than ordinary attacks, even stronger than an Ex Smasher's attack. Below is what an FS Smasher looks like.
http://www.crimson-castle.co.uk/supersmashcards/sets/cards/newcomers/BNew16ROBFSV4.png
Another advantage is that FS Smashers can use any Smash Powers, Smash Bodies and attacks from their previous level, which can give them extra diversity.
However, much like the Ex Smashers, you can only have 1 copy of each FS Smasher in your deck, and it also counts to the same name total as their non-FS variants (e.g you can have 3 Mario and 1 Mario FS but not 4 Mario and 1 Mario FS). Another disadvantage is that you can only play them on top of your Active Smasher and not your Benched Smashers, further limiting how they can be played. Also in addition to inheriting the previous level's Smash Powers, Smash Bodies and attacks, FS Smashers will also inherit the previous level's Prize count. In other words, FS Smashers played on top of normal Smashers will still only give away 1 Prize card, but FS Smashers played on top of Ex Smashers will give away 2 Prize cards when Knocked Out, so they extra consideration for which Smashers you want to play your FS card on top of!
Much like Evolved Smashers, you can't play any FS Smasher cards during your first turn. However, unlike Evolved Smashers, you can still play an FS Smasher card on top of a Smasher you have just played or evolved. But despite sharing similar mechanics, an FS Smasher is not considered an Evolved Smasher unless if their previous level was an Evolved Smasher.
Smasher SP
SP Smashers are personalized Smashers owned by another character. Below is an example of an SP Smasher.
http://www.crimson-castle.co.uk/supersmashcards/sets/cards/newcomers/BNew27CharizardV5.png
The Smasher above is a Charizard owned by Red (who uses the 
symbol). Each owner has their own portrait and symbol. What's special about SP Smashers is they're their own class of Smashers, and their owner's symbol makes them unique. For example, Charizard is classed as a completely different Smasher to a normal Charizard, meaning you could have up to 4 Charizards and 4 Charizard in your deck. However, cards that would normally work on their normal variants may not work on them. A Charizard FS card can't played on top of a Charizard card unless if it was a Charizard FS... Which we have below as an example of a SP FS Smasher.
http://www.crimson-castle.co.uk/supersmashcards/sets/cards/newcomers/BNew10CharizardFSV5.png
Likewise, a Charizard FS card can't be played on top of a normal Charizard card.