What DHCP is
Dynamic Host Configuration Protocol. A protocol that provides a means to allocate IP address dynamically to computers on a LAN. It eliminates the need to assign permanent IP addresses manually. DHCP software runs on servers and can be found in network devices (such as routers) that allow multiple users to access the Internet. Microsoft introduced DHCP on their Windows NT server in 1994. Newer DHCP servers will dynamically update DNS servers after assigning the addresses.
The meaning of Virtual hosting
Virtual hosting is affordable for individual people's Web sites (vanity pages) and small businesses because this technology allows many sites to share the same server (there could be hundreds or thousands of them). The important thing is that no one else has access to your directories. However, unlike dedicated hosting, virtual hosting tends to have more traffic (from the co-located sites) and therefore less bandwidth per site and slower downloads.