What does enchantment - auras mean in magic the gathering?

Answer 1

Aura is a subtype of enchantments and dictates that enchantment is placed on whatever is defined in the rules text of that card; for example if the card said 'Enchant creature' it would come into play enchanting whichever target creature was declared when it was cast.

Creatures are not the only thing that can be enchanted, certain cards enchant lands, artifacts and even players, there is even an oddball aura that enchants a card in your graveyard.

If the target of that aura is removed before the spell resolves, the aura has no legal targets to enchant and will 'fizzle', if the aura's target is removed after it has been enchanted, the aura is destroyed as well as a state based effect.

Answer 2

Aura cards has "enchant" abillites, for example "Enchant creature".

When you cast an aura you must assign a legal target that is correct according to the enchant abillity. When an Aura resolves it enters the battlefield attached to the object it targeted, if it still is a legal target (else it is put into it's owners graveyard). If an aura enters the battlefield without resolving from the stack (put directly into play in some way) it's controller chooses what object to attach it to, it has to be a correct kind of object according to the enchant abillity but this is not targeting, so this will not be stopped by Shroud.

If an aura is attached to an object, and that object becomes unable to be enchanted by that aura, the aura is directly put into the graveyard. This can for example happend if the object gains protection from the aura or the object no longer is the type that the aura can enchant.

Answer 3

Enchantment spells are not Instants. You can only cast Enchantment spells (including Auras) in your own main phases and when the stack is empty.