MS Access was on its way out by the time I started working in software, but the simplest explanation I can give about why the "forms" question is this, let's say you're a business person and...:

  * You have a huge Excel document that's basically a DB. (What Access kinda was)
  * You want users to interact with said data document, i.e add record, find/query record(s), edit records
  * You add a "form" for users to do just that. You can also add a "login" form to give some users more permissions.

Access is an FE for db — JET Red, specifically.

JET Blue aka ESE is currently used by products like Active Directory and Exchange.