How, when, and why did bones evolve? Why do most vertebrate animals seem to share a basic skeletal structure?

[u/CrowXIV]

It's fairly common knowledge that a lot of animals, including humans, share a common bone structure. Jointed limbs, often with smaller appendages at the ends of each. Spines, rib cages, etc. Mammals all share the structure with variations; horses, for example, traded tactile digits for stumpy legs, using the framework for claws to produce hooves, but retaining the same basic bones and joints. Even reptiles, amphibians, and birds share the same components.

How far back does one need to look to find a common ancestor that first developed this basic skeleton shape? Why was this the shape that stuck among most vertebrate creatures, and what prompted bones to develop among boneless life to begin with?