Explanation of marketing environment?

Okay so I am a first year college student in England, currently doing Marketing and Media...we are having a time constrained essay in marketing in March and one of the topics is the following: Briefly underline the current UK marketing environment of Aldi,Lidl and Netto. I havent missed that many classes, but I'm not sure what the broad term MARKETING ENVIRONMENT consists of exactly! What topics should I cover when talking about these discounters? Their targeted customers, their tactics...etc...? Thank you!