The New York Stock Exchange is the world's largest and most liquid securities market.

It's where many of world's largest companies list their shares to be traded amongst millions of investors worldwide; ranging from small individual investors to major financial institutions and governments.

But the NYSE isn't the only exchange. In fact, there are hundreds of exchanges around the world that also work to raise capital for corporations.

And while you're probably familiar with the classic imagery of loud bombastic traders in bright uniforms when you think of stock exchanges, the reality is quite different.

The age of the automated trading machines is upon us and most trades executed today aren't coming from humans but rather algorithmic trading machines.

These computer algorithms (or "algos") come in all sorts of shapes and sizes. But the most controversial of all is known as "high-frequency trading" or "HFT".