For each currency pair, the top graph shows the ratio of long positions to overall positions over time. When the ratio passes the 50% line then there are more long positions than short positions, and when the ratio falls below 50% then there are more short positions than long positions. For example, a ratio of 80% for EUR/USD means that 80% of EUR/USD positions are long and 20% are short.
The bottom graph shows price movements of a currency pair over time. The percentage of change is relative to the price at the beginning/ending of time period.