Web hosting is a service that provides basically storage space on a server and bandwidth which allows the data (web pages, images, emails etc) stored on this server to be transferred to anyone viewing the data using internet browser.
A more pragmatic definition is that web hosting is a service that provides your web site data (web pages, images, emails, etc.) with a connection to the Internet via a web server and high speed internet connection. Your web content is then accessible from anywhere in the world. Renting space on a web server is much like renting an apartment.

Disk space is the size your website can be. Every single letter on your website has to be stored somewhere on your web host's server. Each letter is one byte, and a megabyte is roughly one million bytes.
HTML pages are usually very small, but it is the extra images, scripts, and even databases that can take up large amounts of disk space.
Bandwidth/Transfer is the amount of data the server will allow your site to send or receive in a month. Transfer is usually measured in gigabytes - billions of bytes.

DNS EG is offering Linux system hosting (Windows Hosting is coming soon). Your choice of server platforms should be dictated by the use to which you intend to put it. The majority of web features run fine on both platforms including PHP, mySQL, POP3 etc.
If you intend to create your site using ASP, FrontPage, the .NET environment, Windows Streaming Media, Access, MSSQL, or any of the other Microsoft proprietary technologies then you probably need to use a Windows host.

A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own for use by their clients.

Service scope
The scope of hosting services varies widely. The most basic is web page and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with little processing, we offer this service free to our subscribers.

Single page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, HTML, Javascripts). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also highly recommended.

DNS EG also provides control panel for managing the Web server and installing scripts as well as other services like e-mail.