This is a Shimano XT shifter for an 11 speed drivetrain. It is a trigger shifter that lets you do single or multiple shifts both up and down. The up shift lever can move in either direction to shift. Really a great lever. Sadly I have to go to 12 speed for more range, but I'd prefer to stick with 11 with this shifter. It's really a great shifter. 

Also it has a bar clamp mount so you slide it on your handlebar to install, instead of some newer designs where the shifter attaches to your brake lever.