Loadouts are your equipped weapons and techs. By default, you only have 2 loadout slots, with 3 and 4 being purchasable with EMP.
In each loadout you can equip 2 primary weapons (shotguns, sub-machine guns, assault rifles, sniper rifles, etc.),
1 secondary weapon (pistols and melee weapons),
and 1 grenade.
You can also equip by default 1 universal tech
and 1 co-op tech, unlocking slots 2 and 3 either by getting to level 15 and 25, or buying an unlock item in the EMP store.
If you do not already own a tech, they will appear with a price of emp, rep, or gold. Universal Techs are character modifications that are used in PvP and PvE. Co-Op Techs only effect your character in PvE.