It a members only supermarket for people who work for places like the NHS, Police, Armed Forces etc.
It's to save on food waste etc. so for example the Heinz Baked Beans for 60p may have sausages in them (making them an even bigger bargain) so it's a manufacturing error at the factory where in the past they would have been thrown away. Instead they sell them cheap to the Company Shop. Once I got some washing up liquid (oh the excitement) at half the shop price as one or two had leaked on a whole pallet in the warehouse so they were very sticky - not saleable in the normal supermarkets as they were damaged, but a quick rinse under the tap and they were good as new and the contents on the bottles was not affected.
The 20p Asparagus had yesterdays date on it, but I've still got one pack left in the fridge salad section and it still looks fine. The steaks have tomorrows date on them but they are now all in the freezer and the chicken legs have Tuesdays date on them, but again they are now in the freezer. The crisps have March as their best before date. Some things are even free! Other than what's required to be a member, the only catch is that unless otherwise stated you can only buy a maximum of 6 of the same item so everyone can get a bargain.
Details on membership here:
Membership | Company Shop Group