The gameplay is your standard Battlefield fare. Infantry, ground vehicles and aircraft co-operate and clash in an attempt to wrest away spawn areas from the enemy. The side with more spawn areas not only gets more options on where to spawn, but also has more vehicles immediately accessible and the enemy's tickets decrease faster. Tickets, for those that don't recall or aren't familiar with Battlefield terminology, are used to spawn in. Typically each side has anywhere from 100-400 tickets, meaning that players can respawn 100-400 times. Tickets never increase, they decrease as players die and respawn. Also, tickets will decrease whenever one side has a majority of the flags on a map. The more flags your side controls, the faster the enemy's ticket counter automatically whittles away.
Damage and combat are simplistic for the most part. All units have hitpoints and weak areas, some even have immunities. Hitting a tank from the front does less damage than from the side, and that in turn is less damaging than a rear shot. However, no amount of pistol or rifle ammunition is going to blow an AFV up. Similar rules go for infantry and, presumably, aircraft.
There are various infantry weapons which have varying degrees of recoil, dispersion and damage. All characters will have a pistol and knife, and complement this with a light machine gun, submachine gun, one of a variety of assault rifles, or a shotgun. Then there are the special weapons each class enjoys. These can be satchel charges for the Special Forces class, through a rifle-mounted grenade launcher for the Assault class, healing utilities on a Medic, repair kits and mines for the Engineer, and semi-guided rocket launchers for Anti-Tank infantry. Support troops replenish the ammunition of their friends and I'm sure Snipers do something special too, but we all know anyone playing a Sniper is special anyway.
Actually, to be fair, the Sniper class is actually balanced in the demo. The sniper rifle lacks the more realistic balancing options like gun sway or having its accuracy affected by wind, but it doesn't do much more damage than a regular assault rifle, while at a considerably slower rate of fire. This, along with the presence of vehicles against which the Sniper is generally helpless, keeps the numbers of the pest class at a reasonable level.
In fact, if anything, there are too many vehicles in the game. One of the key criticisms one could level at Battlefield 1942 was that its infantry-on-infantry combat lacked spice compared to Medal of Honor or the later Call of Duty. Battlefield 2 does a much better job at this and despite shortcomings which we'll cover in a second, actually makes for a very decent infantry game. At times, it's almost a shame that vehicles are in at all, with the variety of infantry weapons, the tons of cover in the game and the new and improved movement feel.