Stand : 06.02.2014 (Timeout 5)
Elite - High Anonymous - Level 1 (L1): the web server can't whether you are using a proxy by the information you browser sent.
Anonymous - Level 2 (L2): the web server knows that you are probably using a proxy, but it can't detect your real IP.
Transparent - Non Anonymous - Level3 (L3): the web server knows that you are using a proxy and it can also detect your real IP address.
Socks 4 : Socks 4 proxy will allow working with TCP protocols only, like HTTP (web browsing), NNTP newsgroup access, IRC.
Socks 5: Socks 5 proxy is more advanced, allowing to anonymize UDP protocols as well (ICQ for example).