Nginx has stable and mainline releases.

The even versions are stable. Every year in April the mainline (uneven) version is forked to the new stable branch. The old branch is retired at this time and receives no further bug fixes.

All changes introduced in 1.25.x are now in the stable release, 1.26.

In comparison with 1.24 (stable) HTTP/3 support has been introduced and several fixes.