A Search Engine is a website that allows its visitors to enter a specific search criteria that they wish to find out information, media, products and services. The three main Search Engines are:

• Google
• Yahoo
• MSN

The Ask Network and AOL are still visible but really do not compare with the three main search engines.

The US market share each of these Search Engines has as of May 2008:

• Google 61.8%
• Yahoo 20.6%
• Microsoft 8.5%
• AOL 4.5%
• Ask 4.5%

The above data has been sourced from ComScore.

The UK market share is quite different, Microsoft and AOL are not very popular at all. The following figures are from May 2008:

Google.co.uk    73.42%
Google.com      13.86%
uk.yahoo.com          3.21%
uk.ask.com      2.92%

The above data has been srouced from HitWise.