How many types of VPN are there ? (PPTP VPN, SSL…)

There are two basic VPN types : Remote access VPN and site-to-site VPN.
Remote access VPN allows a user, as it name indicates, to  remotely connect to private networks. The connection happens through an Internet connection that is completely secured.
A Site-to-site VPN also known as Router-to-Router is most commonly used by companies for a corporate use. It is a great option for companies that have different offices located in different countries or different locations. In this case, the VPN 1 acts like a VPN Client while the second one acts like the VPN server. For communication between two servers happens it has to be previously validated.
Regarding protocols, the most common VPN protocols are the following :

• Ipsec (Internet Protocol Security) : security with this protocols works in two phases : it authenticates the session and then encrypts data.
• L2TP (Layer 2 Tunneling Protocol) : A tunneling protocol which is usually combined with IPSec in order to optimize the security of a VPN connection.  L2TP basically created a tunnel between two different connections from this protocol.
• PPTP (Point-to-point Tunneling Protocol) : This protocol basically creates a tunnel to put in the data packet. The PP connection ensures the encryption of the connection.
• SSL/ TLS (Secure Sockets Layer / Transport Layer Security : this protocol is very common in ecommerce sites.
• Open VPN : this protocol is an open source VPN which creates both Point-to-Point and Site-to -Site connections. It also uses another custom protocol based on SSL/TLS.
• SSH (Secure Shell) : This protocol creates a tunnel and the same time it encrypts all data.