Recently browsed is a trail of pages
Opening a title adds it to this browser's recent list. That helps when you remember a poster but forgot to save the film. It does not mean the movie started playing or that you watched it to the end.
My List is a deliberate choice
The heart button keeps a title you want to return to. Save a possibility for later, a series you are considering or several options for a shared evening. You can remove a title without changing the browsing history or its episode checkpoint.
A checkpoint is your own progress note
For television, mark the last episode you completed. Zmov does not receive playback events from the viewing service, so that reminder is updated by you. This keeps an accidentally opened page from being mistaken for a finished episode.
Clear only what you mean to clear
The Recently browsed page has its own clear button. Saved titles and checkpoints have separate controls. If you plan to clear all browser site data, make a list backup first; that broader browser action can remove every local preference at once.