This is the main market in London for publicly traded shares.
The LSE only lets certain companies join its lists subject to them meeting the requirements of its Listing Rules. There are two lists available – the official list for the larger, better established firms and the Alternative Investment Market (AIM) for smaller, faster growing companies that don’t meet the main list criteria. Companies usually seek a listing because it raises their profile and makes raising capital easier. However it also comes with obligations, such as preparing regular accounts and reporting events that may affect the share price to the exchange.