Investors purchase and sell stocks and other shares from one another on secondary markets.
This is what we commonly refer to as the stock market.
The other kind of market that exists is called the primary market.
The primary market is where a newly created stock is sold to the general public.
The creator of the stock sells the shares and receives the money in the primary market.
Anyone can buy and sell any shares on the secondary market as long as there are interested buyers and sellers.