Domain weight is a ranking factor in Google. What is domain weight? Domain weight is essentially the power that can be utilised through having an exact match domain name. For example, say you wanted rank for the term "Learn SEO" and you purchased the domain name LearnSEO.org.uk. This domain is an exact match domain name and Google will more often than not try to rank a website for its main brand query. In this instance the main brand query is "Learn SEO" and as such this website will generally receive a boost in the Search Engine Results Pages around its main term based solely on the weight behind the domain name.
There are quite a few ways to utilise the power of the domain name. Some webmasters compile lists of top volume terms in their particular sector and then perform a bulk WHOIS search to identify whether or not any of the relevant terms are available to register as an exact match domain. For example, if you have an Appliance Repairs website it would be worth putting this term into the Google Keyword Tool and looking at the returned results (always select exact match when performing a query against the Google Keyword Tool). Order the results by Local Search volume and then import them into an excel document. Put these domains into a bulk WHOIS tool and then register any available extensions. You can then build microsites around these terms and potentially leverage the benefit that can be had from the exact match domain name.
There are a few points worth noting when applying this strategy. It is often better confining all of your link building activity on to one site as opposed to diluting it across multiple microsites (it depends on how quickly you want results). It is also worth remembering that this strategy only works for a limited number of domain extensions (or at least the boost is often greater for the main domain extensions). The extensions that should be used in the UK are .co.uk and .org.uk.