Importance of HTTP Methods in a REST Api

Question

I am learning RESTful webservices using JAX-RS Jersey.
Although we have different HTTP Methods for different purposes like:

• GET for Reading a resource
• DELETE fro deleting a resource
• PUT and POST for Creating and Updating a resource.
• PATCH not sure what it is for.

Whats is the purpose of using all these method for specific purpose?

From My understanding every request goes to a method anotated with @Path. I could perform any operation I like in that method.

For Example: I can perform all CRUD operations using only GET requests.

I want know the importance and scenarios where and how I can use these HTTP methods make my REST Api better.

Please point me to right question or link if this is been answered before.