A stage is the column you see and move a task into, and you can name it whatever your work actually calls it — "With the client", "Awaiting parts", "Second read".

A status category is the fixed kind that stage counts as underneath. There are seven: open, in progress, review, paused, done, blocked and closed.

This is what makes inventing your own stages safe. Reports, filters and overdue counts read the category, never the name — so a stage called "With the client" still counts as in progress everywhere it matters, and one you mark as done still closes the task off. Get the category right and you can name the stage anything.