Casting a spell is usually an action, unless stated otherwise in the spell description.  You can only use one Spell that uses a Spell Slot a turn, plus one cantrip.  Although you can cast a Reaction based spell on someone else's turn.<br/><br/>Misty Step is a spell that allows short range teleportation and it is a bonus action.  There is also a cantrip called Soul Step that allows teleportation, with limitations, that is also a bonus action, it comes from the Sword Coast book if I remember quickly.<br/><br/>So if someone had Misty Step, they could teleport and make a weapon attack or attack with a cantrip.  Or with Soul Step, can teleport as bonus action and then use your action to cast a spell.