Stands for "Virtual IP Address." A VIP (or VIPA) is a public IP address that may be shared by multiple devices connected to the Internet. Internally, each device has a unique local IP address, but externally, they all share the same one.
VIPs are common in home and office networks. When a device connects to the network, the router assigns it a unique local IP address, typically via DHCP. Examples of local IP addresses include 192.168.0.2, 192.168.0.3, etc, with the router IP address set to 192.168.0.1. Some routers use the IP address 10.0.1.1 and assign IP addresses 10.0.1.2, 10.0.1.3, etc. Local IPs are merged into a single public (or "virtual") IP using network address translation (NAT). The virtual IP address is what identifies the devices on the Internet.
VIPs are also used by servers. For example, multiple web servers may share the same IP address, allowing them to distribute requests across multiple machines. This is useful for load balancing and redundancy, A "high availability" server, for instance, may have a single IP address shared by two separate computers.