The difference is that the Inline form is mainly used to edit data in the database after doing a search.
When a user changes the data through an inline form template then the changes are saved directly (no save button).
When a specific search is done, the results are shown in the summary.
In the summary, the edition can be activated. This allows the user to edit the data of that specific record in the database.
When the user clicks on the Edit button, the Inline form appears.