Ingate VPN supports IPSec and IKE, which are standards developed by IETF (Internet Engineering Task Force). More and more software developers base their products on these protocols. You can read more about IPSec and IKE in appendix E, More about VPN.
Ingate VPN also supports PPTP connections, another protocol for making private connections over insecure networks. You can read more about PPTP in appendix E, More about VPN.
Authentication is the process of making sure that the message you receive really originates from the right sender, and that it hasn't been corrupted during transmission. Authentication also protects against resending of packets, but not against eavesdropping.
Encryption is the process of distorting data so that only the desired receiver can read the message.
Different methods of authentication and encryption exist. Ingate VPN supports the authentication algorithms MD5 and SHA-1, and the encryption algorithms 3DES (triple DES) with a key length of 168 bits, and AES with a key length of 128 bits.