An early day motion (EDM) is a motion, expressed as a single sentence, tabled by Members of Parliament that formally calls for debate "on an early day". They act like petitions amongst MPs that are not ministers.

From edmi.parliament.uk:

Early day motions (EDMs) are formal motions submitted for debate in the House of Commons. However, very few EDMs are actually debated. Instead, they are used for reasons such as publicising the views of individual MPs, drawing attention to specific events or campaigns, and demonstrating the extent of parliamentary support for a particular cause or point of view.

See also