Alpha squad Information
Alpha Squad is the get in then get out squad, the light squad, mainly Recon.
There light armor and weight, fast moving abillitys give them advantages over locations.
There main job is the capture the ghost as quick as possible while the other squads give them support from certain locations.
Bravo squad Information
Bravo Squad is the frontal attack squad, the ones that are mainly for penetration, medium weaponry.
Bravo squad rushes in and takes out enemies as the other squads give support from flanks.
Charlie squad Information
Charlie Squad are the snipers of the squads, they are medium/light/heavy, they can consist of different classes as most classes use Snipers, They stay behind and take out enemies that are to far or unreachable from different squads.
You don't just have to always use the class you assign your self to, its just the one you normally use and are good with.