From Traderpedia

An intermingling of buyers and sellers with the intent of executing transactions

The financial markets can be divided into different categories:

These markets can be either primary markets or aftermarkets or secondary markets. Newly formed (issued) securities are bought or sold in primary markets. Secondary markets allow owners of the security or the product of securities to buy or sell the same.

There are various different types of orders that can be placed in the markets and a brief definition of some of these can be found in Order Types.