You or a creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person.
This description omits the very important third sentence: "The spell ends for a target that attacks or casts a spell." We just almost lost a party member because we didn't know that.
I think you're mistaking this page for the 2nd level spell "Invisibility". This is "Greater Invisibility", a 4th level spell, and the ability to attack and cast spells while remaining invisible is the "greater" part (they don't seem to represent the change in duration in the title).
A ha! Indeed, between myself and my DM we were reading two different entries. Thanks for the clarification.