clarification: Database, DBMS, SOA, REST

Hi everyone I’m new to server-side technologies so maybe this is a bit of a dumb question but after reading dozens of articles and viewing dozens of videos I’m still very confused. This has to do with arquitecture principles of modern apps.

Relational model: I know that a few years ago the model was to have a database (mostly relational) and a DBMS that enabled the connection between an app and the database.

Question 1: Since we are talking about a relational model some examples of DBMS’s are MySQL or PostgreSQL? Question 2: What is the process of information exchange? The client-side uses a language like PHP to make a request to the server and then the DBMS transforms the request into SQL and accesses the database? Is the conversion of the PHP into SQL part of DBMS function or another server-side software is needed? (If someone could provide me summary detailed explanation I would be very thankful)

Non-Relational Models:

Question 2: Nowadays with the rise of NoSQL models does the same concept of DBMS apply? Since these systems allow other querying language other than SQL there should be some piece of software that has this function?

Service Oriented Arquitecture: Almost every app uses this type of arquitecture. I understand the concept of avoid the creation of too tight software relation between client and server side allowing for multiple use across several platforms. What I don’t understand is what parts constitute a system that is build this way.

Question 3: Does the DBMS provides the API’s that constitute the web services made available?

Web Frameworks: Last but not least, where do frameworks like Django or Ruby on Rails land on?

Question 4: These are supposed to provide tools to develop everything between the front-end and the database of a SOA system right?

Question 5: I’ve seen a lot of buzz about REST arquitecture. Can you explain me of the querying process happens and what are the software entities involved.

Thank you in advance for any explanation that helps me understating these questions. Please provide some links or any diagrams that you find useful.