What is the market in economics in detail?

In detail, it is just you. What you buy, what you sell. Food, rent, transport costs, clothing - and usually you just sell your time cum expertise, if you are a common or garden “wage slave.” That is your ecopnomy, and you know it down to the last penny, if you bother to keep all the paperwork.
Your neighbour has a different detail economy: his tastes are different, and he has different skills. Maybe he earns more, maybe less. And the next man down the road, and the next. Keep going for the next seven plus billion people, and you have just about tied up the whole world’s economix. But try not to keep ALL the paperwork - your house will subside.
Also, after the first few thousand, your mind will boggle, your eyes will glaze, you will not be able to remember why you started this, and you will realise that you can have too much detail.