Question: I am developing an ADF Fusion Web Application and I want to be able to update and save the changes about entities into my database. Do I always have to drag and drop both Submit and Commit buttons together? I can not unserstand their difference implicitly.

Answer: 
The submit button actually does nothing special, it just does a submit of your form (like in normal HTML). It's the same functionality as every other button (except if you start using the immediate attribute, but not considering this here). The data from your form (or input components) will then be 'saved' in your model (so your entities). But not in the database of course.

When using the commit button, a submit happens (so everything for above happens) and then your data will get committed (saved in your db).
User404 is correct. Lets go one step further. A lot of people do not want *separate* submit and commit buttons. [This](https://community.oracle.com/thread/2402124?start=0) may give an example of calling the commit programmatically from the ActionListener event handler of a button.