The multihop add-on routes your traffic through two datacenters and encrypts your traffic one more time.
Multihop prevents timing-attacks drastically as attackers are forced to tap into two different datacenters, in two different cities simultaneously.
The traffic is routed through two cities in Sweden - Stockholm & Malmö.
Your internet speed will decrease since the traffic is passed through multiple cities, but your anonymity and integrity will be substantially enhanced.
The last VPN server in the network chain does not have access to your IP address as the first VPN server routes the traffic to the second.
OVPN also takes physical security seriously. All servers used for VPN tunneling operate without hard drives and are therefore incapable of logging any traffic.