The mark, lockups, and a maskable icon, ready to use — SVG for anything that can take it, PNG for anything that can't. Black or white ink on transparent, or a single dual-mode "background" file that switches between the two automatically with the viewer's system theme (and falls back to a light background wherever that's not supported — uploads to GitHub and most other icon fields, for instance).
The symbol on its own — for tight UI placements. Not maskable-safe; see Icon below for that.
Maskable — recentered and scaled to fit a circular safe zone, for app icons, PWA manifests, and profile/avatar uploads (e.g. GitHub) that crop to a circle or rounded square.
Mark and wordmark side by side — the standard nav/header lockup.
Mark above wordmark — for square-ish placements like social avatars.