Watch this video for what is an EPP code or Authorization Key for a domain
Extensible Provisioning Protocol (EPP code) is a protocol used to officially transfer a domain from one registrar to the other. An EPP code (also referred to as transfer Authorization Key, Auth Code, Authinfo Code, Authorization Transfer Key or an EPP Authentication Code) is a secret code required to initiate a domain transfer request from old registrar to the new registrar. The EPP code secures your domain from unauthorized transfers, it protects your rights as a domain name owner. Being the owner of the domain, only you have the authority to transfer the domain to other registrar. To transfer the domain, the EPP code has to be provided to the new domain registrar so that they can initiate the domain transfer request and get the domain transferred under their registry.
How to obtain an EPP Code or Domain Transfer Authorization key?
To transfer .com, .net, .org, .co.in, .in, .biz, .mobi, .info, .us, .tv, .cn, .com.cn, .net.cn, .org.cn, .cn and .tw domains you will need EPP code. If you want to transfer one of these domains then you will have to contact your current domain registrar they will provide you the EPP code of your domain name. Once you get the EPP code forward it to your new domain name registrar, they will get the domain name transferred to them. You will be charged for the domain transfer.