The only way to build combat-unit factories (Kbot Labs, Vehicle and Aircraft plants, Shipyards)
Besides building, it can repair, assist factories and directly build mobile construction-assistance & scout units (Arm FARK and Core Muskrat)
Outposts start at Tier 0 and can be morphed up to Tier 4, when they're able to build the almighty experimental factory
Outposts spend energy for merely existing, so unless you're floating energy it's usually not a great idea to "spam" (build many) of them to "assist" (speed up) construction. Initially FARKs are best suited for that role, at least until they start clumping and disturbing unit production.
Besides building, it can repair, assist factories and directly build mobile construction-assistance & scout units (Arm FARK and Core Muskrat)