A place where buyers and sellers meet to trade goods, services, or information. This can be physical or virtual.
When people mention "The Market", they often are referring to the United States equities markets. However, a host of other assets have their own markets. This includes bonds, commodities, and derivatives. The largest market is FOREX which is the trading of currency.
Cryptocurrency has its own market also.
Commonly, exchanges are used for swapping. Within cryptocurrency, we are seeing the establishment of decentralized exchanges.
Markets make it easier for buyers and sellers to find each other. Another important features is markets can often provide liquidity. This allows sellers to turn their assets into cash.
Without markets, individuals would be responsible for finding someone interested in what they are selling. This would be a time consuming process with no guarantees of success.
Due to technology, markets are typically global, depending upon what is being offered. Anything that is digital can have transactions with people all over the world.
It was also due to this that transaction fees came down. In the past, especially with financial transaction, the fees for conducting business were high. Stocks, bonds, and derivatives all cost a fraction of what they use to in terms of the fees. In fact, many brokerage firms did away with the commissions on stock transactions.