Search engine rankings can have a massive effect on how well your website does and the sale and / or enquiries you get through it. The main search engine used today is Google with others such as Bing and Yahoo coming in a little way behind. Each search engine will have a different set of criteria that it uses in order to determine the rank of a website but all of them are very similar and if you do well on Google you tend to do well on the others too.
You need to keep an eye on your website rankings as his can show you if there is an issue with the site you need to sort out or if a change you have recently made has had a positive or negative impact on your search engine results. You can check rankings manually or you can use software that will check them for you. Be wary when using third party software and be sure to double check a few of the results yourself to ensure that they are accurate as often they will be misleading. Many of the companies that offer this software are based in the USA so you need to ensure that the results you are been given are for the UK search engines.