In England, Wales and Northern Ireland, a town traditionally was a settlement which had a charter to hold a market or fair and therefore became a "market town". In Scotland, the equivalent is known as a burgh (pronounced [ˈbʌɾə]). There are two types of burgh: royal burghs and burghs of barony.
The Local Government Act 1972 allows civil parishes in England and Wales to resolve themselves to be Town Councils, under section (245 subsection 6), which also gives the chairman of such parishes the title 'town mayor'. Many former urban districts and municipal boroughs have such a status, along with other settlements with no prior town status.
In more modern times it is often considered that a town becomes a city (or a village becomes a town) as soon as it reaches a certain population, although this is an informal definition and no particular numbers are agreed upon.
The cultural importance placed on charters remains, and it is not an unusual event for towns across the UK to celebrate their charter in an annual Charter Day (normally a fair or mediaeval market).