First i explain about
Client Side --  The Enduser who is performing the task or updating some info or client place

ServerSide -- It is the place where the website is deployed with some logic to happened after a request from a particular client to make some changes or give some info to client

Client Validation can be performed using Javascript ,PHP,PerlScripting ,
Serverside Validation can be done using the logic in which we write using ASP,ASP.Net or JSP or etc .