OHLC stands for Open–High-Low-Close. This type of chart is typically used to illustrate movements in the price of a financial instrument over time. Each vertical line on the chart shows the price range (the highest and lowest prices) over one unit of time.
On the below example the amount of price changes over the minute do not range above 295. The number in the top left shows the count of price changes during that time period. For the example below it is showing how many changes for the current minute.