The EVA Jetpack is an inventory item that lets Kerbals use the jetpack. As of 1.11, the EVA Jetpack must be equipped in order to jetpack while in EVA.
The EVA Jetpack contains 3 units of monopropellant. A Kerbal wearing a jetpack has approximately 350 m/s of delta-V.
EVA Fuel Cylinders can be used to carry more monopropellant.