Tick chart

Tick chart for SP500, showing each change in the ask or bid price. (If the spread is very tight then the lines may overlap, and only the ask line may be visible.)

As well as a plain tick chart, you can use the "Tick speed" mode to add an indicator showing how long it has taken for the last N ticks to happen. The lower the histogram, the faster the market is moving.

The "Timed" mode still shows each change in the ask or bid price, but the X axis of the chart is set to constant units of time. You can use this to view individual ticks while still being able to distinguish between fast and slow periods in the market.

The "Candles" mode draws tick candles. These are candles which form each time that N ticks happen, rather than being time-based.

About SP500

The S&P 500 is a share index of 500 large companies listed on stock exchanges in the USA. It is one of the most widely followed indices in investing all over the world. However, unlike other indices, its constituents are not based solely and automatically on market capitalization (largest companies), but are instead subjectively selected. This has led to people asserting that the S&P 500 is more like a managed investment fund than a typical share index.