What counts as a revision, and what counts as new work?

One confusing part of freelance work is revisions.

Sometimes a client asks for a small change.

Sometimes they ask for a completely new direction, new content, a new layout, or a different version of the same work.

Before work starts, how do you define what counts as a revision?

For example:

• fixing small mistakes
• changing wording or layout
• adding new sections
• changing the original brief
• asking for a different direction
• requesting another version after approval

Where do you personally draw the line between a revision and new work?