DNS (Domain Name System) is a system that converts domain names into IP addresses on the Internet. If you type the domain name (example www.yahoo.com) in the address bar, in the background the request goes to DNS servers of your ISP (Internet Service Provider) then these DNS servers translates the URL into an IP address (example 87.248.113.14). Sometimes, while doing this conversion there may be chance of slow internet speed.
Without DNS, you would have to type the four numbers and dots into your browser to retrieve the Web site. You can type it for a single domain, but in case of many, it would be awkward to memorize the IP addresses.
Here is an alternative DNS resolution service to your Internet service provider's DNS service. OpenDNS is a free DNS resolution service that makes you the internet safer, faster and reliable.You can enable the OpenDNS in your computer from TCP/IP Properties section by following this manner.
Control Panel -> Network Connections -> Local Network Connection -> TCP IP Properties. Then click the radio button and use the following DNS server addresses.
208.67.222.222
208.67.220.220
OpenDNS offers you Phishing Protection, Domain Blocking, Typo Correction and Shortcuts features. If you type Bharatstudent.cm instead of Bharatstudent.com then it corrects the type mistakes automatically. The speed increase in browsing can be noticeable with requests that are not stored in local cache.
source:OpenDNS Lifehacker