SpaceX

u/675longtail on Reddit summarized it:

It includes a Starship development timeline, starting with an orbital flight attempt in Q3 2023 but moving on to detail:

Q1 2024: First Starship launch with payload

Q3 2024: Successful recovery of the "Starship system"

Q3 2025: On-Orbit Propellant Storage System Preliminary Design Review

Q2 2026: Starship On-Orbit Servicing/Recovery/Docking Concept Review

Q2 2027: Crew Starship Ascent, Entry, and Landing Concept Review

Q4 2028: Starship LEO crewed space station Preliminary Design Review

And lots of other tasks too. (For example, I have no idea what "a human health countermeasure tech demonstration" might be.)

A Space Act agreement doesn't involve payments between NASA and the company. But it does involve NASA and the company agreeing to do specified space-related things, where NASA will

Provide access to requested NASA technical data, lessons learned, expertise support, services, facilities, equipment, and NASA-developed technologies, on a non-interference basis as resources permit.

and SpaceX will "Provide NASA with data regarding its progress towards the milestones", meet periodically, and provide equipment if required under agreed Technical Implementation Plans.