Here we have two series of numerical points (so there is no text key, we have numerical values on both X|Y axes) that shows us how varied the exchange rate in the last 700 days.
On X-axis we can see the day from which the sample value was taken, on Y-axis we can see the exchange rate of that particular day.
Just looking at this graph I definitely can say that EURO began to appreciate against the DOLLAR until the day 613, but after that point the DOLLAR began to gain back its value.
On the other hand what was happened with the UK quid was exactly inverse. Without being a financial analyst I can say that EURO began to lose its value in the last 100 days.
Oh, there is something more: if we are trying to find the best fit between these values then the regression line (that green thin line) is going to help us, because it shows us the trend of this values. Maybe a better use for this line we will see when we talk about scattered sample values (see scattered points chart).