Manga chapters come out online and/or in physical magazines, they are then bundled in a volume, that volume usually comes out 1-2 months after the last chapter of that volume.
It usually comes with extras, usually an Homake, an epilogue, an after story.
People tend to look at volume releases for either uncensored (or less censored) drawings and/Or a more satisfying ending, for example people hoping for something like with "Dress up darling" or how My Hero Academia tried to salvage things a bit by adding a lot of exposition.
I hope I don't sound patronising.