A REST webservice would normally support four HTTP verbs GET, POST, PUT and DELETE.
Simply putting, the verbs have following function.
GET: requests some information from server.
POST: sends/ posts some data to application.
PUT: requests that sent data to be put under given URI location.
DELETE: Deletes the given entity.
Most common of these are GET and POST, as they can mostly handle all the requests.
Another interesting debate is when to use PUT and POST as both tend to send some data to server. Ideally, when we know exactly where to add the data, we will use put, and if we want application to take a call, we will use post. For example if I want to add/ edit user id 112, I will use PUT. But if I just say add a user and let application assign the id, I will use POST.
More on PUT vs POST-