WhoIs is a protocol used to query databases about the registration of various internet resources — most commonly domain names and IP addresses.
WhoIs searches are available on most web hosting sites, and can be used to check the availability of domain names and the information stored in the database about the registrant/owner of a given domain name.
If a Domain Name is already registered, a WhoIs search will give you the details of whom it is registered to.
If it is not registered no details will come up this it is an available registration.
The Pickaweb Whois can be found at https://www.pickaweb.co.uk/domain-names/
If you are concerned about privacy & you do not wish to have your details published on the whois then it is possible to hide your details. With UK domain names (eg: .co.uk, .org.uk) you can select the confidentiality option via the Pickaweb Domain Name Management Area.
With Domain names (eg. .com, .net, .org, .biz, .info) it is possible to order a Whois Privacy service. This costs £4.99 per domain name per year.
The Whois search will also show you some very useful information such as the Nameservers of the domain. Basically this helps you to identify which physical server your domain is hosted by.
If you need to make changes to your domain name you can do this via the Pickaweb Domain Name Management Area.