There are five different skill trees in Starfield, each one of which has sixteen or seventeen unique skills. If that weren't enough already, every skill in Starfield is broken up into four ranks, with higher-ranked skills providing larger buffs, and in some cases, granting access to brand-new perks entirely.
Starfield: How to Upgrade Skills
There are 82 skills in Starfield, each of which has multiple ranks. This guide will explain how to upgrade skills and the prerequisites for doing so.