Matting is the material that mats are made from — rough, strong, woven stuff, often made from grass, straw, coconut fibre, rubber, or plastic. It is an uncountable noun: you say 'some matting' or 'a piece of matting', never 'a matting' or 'two mattings'. Think of it the way you think of 'carpet' or 'cloth': the material itself, sold in a long roll, before anyone has cut a mat out of it. So a shop sells matting; you put a mat by your door. You meet the word most often with the material in front of it — coconut matting, rush matting, rubber matting — and in places where the floor needs to be tough or non-slip: doorways, gyms, boats, greenhouses, market stalls. It also gets used for large pieces laid flat on the ground even when nobody would call them 'a mat', as in 'the floor was covered with matting'. It is a fairly plain, practical word, not a formal one. Separately, 'matting' can be the -ing form of the verb 'to mat' — when hair or fur gets tangled into thick lumps ('the dog's fur was matting'). And in picture framing, the 'matting' is the card border around a photo. Those are less common; the material is the main meaning.