Create SQL Database

You can have any # of SQL DBs. You pay for each one. The purpose of an elastic pool is to allow you to have several DBs that effectively share the same resources. The primary use case is for databases that have varying degrees of use such that having each DB be standalone is not cost effective.

Imagine a scenario where you have 3 different DBs in your system. The first is used all the time whereas the second is used only at the end of the month and the third is only used at unpredictable points in the month based upon business meetings. Having all 3 DBs standalone means you have to manage each one separately. The first DB probably needs higher utilization to handle the constant workload. The second DB only needs to "scale up" at the end of the month. The third DB is unpredictable. Unless you know when that is going to occur you probably aren't going to be able to "scale up" fast enough. The workaround would be to allocate more resources then you really need for the third DB, just in case. But this is wasting money and resources. Elastic pools allow you to combine DBs into a single resource that you provision for both. In my example the second and third DBs might do better to be in an elastic pool. The pool will scale up if either DB is getting heavy use. Assuming neither DB is getting hit hard at the same time then you are effectively running 2 DBs in the space for 1. This reduces costs.

Of course you'd want to do profiling and determine if this is the best approach or not depending on each of your DBs. A DB that is used constantly (e.g. the first DB in my example) probably wouldn't gain anything by being in a pool. You can add and remove DBs from pools as needed so you can start with a DB standalone and then add it to a pool if it is not using resources efficiently.

Read more about elastic pools here.