For the first time in a BioShock game, plasmids (now called vigors) and guns aren't the only things you'll be equipping. There's a ton of gear in BioShock Infinite, and you'll be finding new pieces and switching them out all the time.
You can have multiple pieces (gloves, hats, etc.) equipped at any given time, and although they don't affect Booker's appearance (it's a first person game. Duh), they can vastly alter his abilities. One piece of equipment causes his melee attacks to light enemies on fire, for example, while another causes certain elemental attacks to chain together through multiple enemies.