The entirety of the Beginner+ guide is preparation for this mode – and a very abridged version of that is the Solos description.
Duos and Squads is very much the same as Solos, except that one can play as a part of a party of up to two or four players respectively.
Since you aren’t playing alone, it is a good idea to come to an agreement as to where to land, as the squad that sticks together and cooperates has a higher chance of getting out of things together than any group that does not.
Since one has actual team mates in this mode, chemical-based healing weapons are more useful than in solos where emus are the only legitimate beneficiaries.
A further important difference in Duos and Squads, is that an ally who is taken to zero health is not immediately killed but instead enters a downed state, from which they may either be revived or they may perish to either exposure or the attention of enemies.
The last team to survive wins. All else is the same.
‘Next’ we’ll be looking at Mystery Mode (which is not active as a mode).