SAP S/4HANA 1709 - Difference between EWM, WM and SCM EWM Configuration Nodes!

Greetings Experts!

As there is a requirement from our client to implement Warehouse Management module, I was exploring on the same and found that there are three configuration nodes (SPRO) for implementing Warehouse Management! With reference to the same I've the following queries, kindly help me to understand them;

1. What is the difference between each configuration nodes/ functionality?
2. Our system is S/4HANA 1709 and currently running modules are MM, SD, PS and FICO. If we want to implement WM, do we need to buy any separate licence from SAP?

Thanks,

Pavithra