This description is provided by Olive Thexton of Fylde Branch

IGI: International Genealogy Index 

This is produced by the Church of the Latter day Saints (also known by some as the "Mormon Index") and records births, marriages and deaths, usually prior to 1837.

It is an index on microfiche, alphabetical by name within each county, of SOME Parish Register entries - the quantity increases with each successive edition. 

Main local libraries have the Lancashire listings, with some of the larger reference libraries having wider geographical coverage. 

Whilst the IGI is a very valuable research tool remember that, like any other copied list, it has errors and is incomplete. It may show marriage banns, which were 'read out' in Church, but the marriage never actually took place. Newer entries are not being fiched, but are only being entered into the internet version of IGI.