Yes, you're right on that. In warmahordes, you can move around freely, you can walk into combat if you want, or walk out of combat (taking a free strike if you do). You can even run in, if you don't mind being unable to attack for the turn - great for tying up ranged units/jacks. Basically, just move, and, if you're within your melee range, you're in melee. Simple as that.
Charging is basically a manoeuvre that allows you to get an extra 3" range when moving in to attack, and gives you a Boost on the first damage roll against your charge target. There are restrictions placed on it (you must try to move into melee distance, and if you fail, you lose the rest of your action, you can't use a Power attack, must make a melee attack, ect.) but that's the crux of it.
Hope that helps