DHCP - The Dynamic Host Configuration Protocol (DHCP) automates the assignment of IP addresses, subnet masks, default gateway, and other IP parameters. 
When a DHCP-configured client (be it a computer or any other network aware device) connects to a network, the DHCP client sends a broadcast query requesting necessary information from a DHCP server. The DHCP server manages a pool of IP addresses and information about client configuration parameters such as the default gateway, the domain name, the DNS servers, other servers such as time servers, and so forth. Upon receipt of a valid request the server will assign the computer an IP address, a lease (the length of time for which the allocation is valid), and other TCP/IP configuration parameters, such as the subnet mask and the default gateway. The query is typically initiated immediately after booting and must be completed before the client can initiate IP-based communication with other hosts.
HTTP - HTTP is a request/response standard between a client and a server. A client is the end-user, the server is the web site. The client making an HTTP request – using a web browser, spider, or other end-user tool – is referred to as the user agent. The responding server – which stores or creates resources such as HTML files and images – is called the origin server. In between the user agent and origin server may be several intermediaries, such as proxies, gateways, and tunnels. HTTP is not constrained to using TCP/IP and its supporting layers, although this is its most popular application on the Internet. Indeed HTTP can be “implemented on top of any other protocol on the Internet, or on other networks. HTTP only presumes a reliable transport; any protocol that provides such guarantees can be used.”
DNS - The Domain Name System (DNS) associates various sorts of information with domain names; most importantly, it serves as the “phone book” for the Internet by translating human-readable computer hostnames, e.g. http://www.example.com, into the IP addresses, e.g. 184.108.40.206, that networking equipment needs to deliver information. It also stores other information such as the list of mail exchange servers that accept email for a given domain. In providing a worldwide keyword-based redirection service, the Domain Name System is an essential component of contemporary Internet use.
For More Details -