Lidl has a smaller 'stock' than the big stores, and generally only have in pretty much general items, so whilst you may find common items there, you wont find anything specific to a narrow market, so no 'free from' dedicated area, no area dedicated to specific global areas (ie chinese, indian/etc) and limited varieties of what they do stock.
so for example :
Crisps : Lidl has a small section, primarily the own brand, but then some walkers/etc and maybe a box or 2 of special items. Asda, 2 long sections, own brand, and probably 3 or 4 other brands, various pack sizes, offers, specialties of things like popcorn, again multiple flavours and brands.
Canned items : Lidl - small section of commonly bought items and nothing really unusual, asda, probably has more soup varieties and space than the whole of Lidl has for everything.
Drinks, Asda has 1 row of boxed beers, 1 row of bottles (craft as they like to call it now :/) 1 and a bit rows of wine,1 row of spirits, plus end shelves of offers and cider and others about 1/2 row. Lidl, about 3 meters space of beers, and loads of wine, but still about 1/3 of asdas (BTW lidl 89p bottles are really nice, try them!)
Also the central sections of lidl that change weekly, this is also used to et people in as well, and some good offers sometimes.