There are two ways in which the browser can send information to the server,
1) GET Method and
2) POST Method
1) GET Method
The GET method sends the encoded client information appended to the page request.
Each request informations are separated by the question mark (?).
You can only send upto 1024 characters by GET method.
You can not send binary data like images or documents through GET methods
You can access all the data using QUERY_STRING which are send via GET methods.
2) POST Method
POST method transfer client data via HTTP headers.
There are no limit on data size.
You can also send Binary data such as images or documents.