Server Side Code
Server side is the code that resides at web server.
For every client request code is executed at server side and result is send to the client in simple HTML format.
Performance is lower than client side code due to server round trips.
Client cannot see the business logic though it is stored on server.
Client Side Code
Client side code is reside at client's browser itself. It is executed at
client side only. User can easily see the code by View - > Source option.
It is generally used in validation form like text field is empty or not, email address validation etc. It is faster than server side code.
Server side code is responsible to execute and provide
the executed code to the browser at the client side. The executed code
may be either in XML or Plain HTML. The executed code only have the
values or the results that are executed on the server. The clients
browser executes the HTML code and displays the result.
Where as the client side code executes at client side and displays the result in
its browser. It's the client side core consist of certain functions that
are to be executed on server then it places request to the server and
the server responses as the result in form of HTML.