Design help. I need to make a centralized database with details of all the users. The details should be used across many applications

Consider I have two applications that need to access user information from a common database.

The applications need to be something like this.

• app1.domain.com
• app2.domain.com

Both of these applications should be able to use the same database, say users.

How do I make that happen?

Also, I do not know about the ReST api. Is this the right place to use them?

I'm a beginner. Please help! Thanks!