What does the -dev prefix mean in the composer version number of a package?

Question

PHP

Good evening,

Many composer dependencies specify the dev-master version. Does that just mean the master branch?
What does 2.3-dev mean and how is it different from just 2.3?

Or, where can I read about it? I can’t find a sane explanation in any way, I’m tired of specifying versions of dependencies and not understanding what they mean.

Answer 1

The -dev version contains the header and other files required by the programmer if he wants to extend it himself.
Source

Answer 2

dev-* means branch. dev-master - master, dev-bugfix - bugfix branch.
2.3 most likely means a tag in git'e or just an alias of some branch.
Source