because it simple...

what is proxy, proxy check, what is proxy site

Main content page - what is proxy.Transparent Proxy - This type of proxy server identifies itself as a proxy server and also makes the original IP address available through the http headers. These are generally used for their ability to cache websites and do not effectively provide any anonymity to those who use them. However, the use of a transparent proxy will get you around simple IP bans.
Anonymous Proxy - This type of proxy server identifies itself as a proxy server, but does not make the original IP address available. This type of proxy server is detectable, but provides reasonable anonymity for most users.
IP is the usual abbreviation for Internet Protocol. It is also a common abbreviation for different things in different fields.
An Internet Protocol (IP) address is a numerical identification (logical address) that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes.
Although IP addresses are stored as binary numbers, they are usually displayed in human-readable notations, such as for IPv4, and for IPv6. The role of the IP address has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."