Not all graphs give information about the past: some give estimated figures of future data. For example:
This graph shows the population of the United Kingdom from the year 2005 to the year 2050 measured at five year intervals. But the only figure which we can be sure about is the one for 2005 (59.9 million). All the other figures are in the future and they are estimates (what we, or the population statisticians, think the population will be). These estimates are called projections. So we can say that the UK population is projected to rise to just under 65 million in 2035. In 2040 it is estimated to remain at just under 65 million, after which it is projected to decline.
You can see that it is important to look at the axes in order to decide whether the data in the graph is a projection or not.
Sometimes projected data is indicated by a dotted or dashed line, as in the following example:
Here we can see that the population of Denmark is projected to rise to 5.5 million in 2010, after which it is projected to remain stable.