Overview & Obtaining
Tribalwear is the only neolithic garment in RimWorld, and covers the torso, neck, and legs. Tribalwear requires 60 resources to make, less than the 80 required to make a set of T-shirts and pants. As well as providing some insulation, Tribalwear will remove the 'Naked' thought debuff from both genders of colonist. Tribalwear can either be crafted, or stripped from Tribal raiders.
As a neolithic garment, tribalwear can be constructed at a crafting spot, or tailoring bench - the former option not requiring any research whatsoever. A piece of tribalwear requires 60 of any textile, and 30 seconds of work (1,800 ticks) to be created, assuming baseline global work speed, consciousness, sight, and manipulation.
Conclusion & Comparison
Tribalwear insulates better than a set of pants combined with a button-down shirt (10 Degrees Celsius vs. 7), but tribalwear offers absolutely no protection unless made from a material which offsets protection (e.g. Devilstrand). Additionally; armor vests can't be worn on top of tribalwear, as tribalwear occupies the on-skin and middle slots for apparel. Therefore Tribalwear should only really be made early-game when you start getting new colonists (which may not be sufficiently clothed), and when you typically won't have many textiles in storage yet - or when in crisis where you desperately need new clothes and there are no other alternatives (extreme case).
Tribalwear is ideal for prisoners though as it offers essential bodily coverage, it's cheap, and also offers no protection: making prison breaks easier to deal with as prisoners can be downed easier (especially important through mid-late game when enemies frequently spawn with armoured vests). You can force prisoners to wear tribalwear by stripping them before capturing, and then ensuring there's a higher priority stockpile specifically for Tribalwear in their cell/barracks.
The following table(s) will display how good some normal quality Tribalwear is at insulating when made from various materials...