This article contains spoilers from the most recent DCEU film. You have been warned.
It is a four-treaded tank with each tread on a separate leg so it can walk. It’s special function is that it can pierce into surfaces with each leg to climb up walls or hang from a roof. Its cockpit interior is based on function, like a forklift. It has one command seat and two fold-out benches. 
The Knightcrawler also has powerful weaponry for dealing with powerful alien threats, as seen when Batman used the vehicle's powerful Gatling guns to tear through a Parademon's armour and flesh. This addition of such weapons was likely added in order for Batman to stand a chance against the Parademon threat facing the Earth.