Markets exists everywhere, i.e. in every locality and work with proper procedure and time. Although, it is not compulsory for one to go to the market to buy goods. Orders can be placed on phone or through internet for variety of things and goods are delivered at our door steps.
For instance, there are sales representatives waiting for doctors in clinics and nursing homes, they are the people involved in the selling of goods. Hence, buying and selling can be done through various ways and not necessarily through shops in market places.
There are some markets that we don't recognise because there are goods which are traded but we don't use them directly. It means we don't normally see buying and selling but only the final product like the car in showroom.