Here's the just of it:
Engaged (connected), the bar allows for a more stable highway/street drive. Disengaged (disconnected), it allows your vehicle to articulate more and your tires to bite better despite the offroad terrain.
Google is your friend! Google to research it some more, and your questions about it will be answered.
2010 Ranger FX4, 5 Spd. Manual, 4:10, 32" Goodyear MTR's (Kevlar), PreKeys & Crank, BellTech 6400 Shackles, K&N drop in, Leer 100XR, Krown Rust Proofed, Line-X BedLiner (over rail), Ford Factory Bed Extender.