A line graph is way to visually represent data, especially data that changes over time. Let's take a look at an example. Created by Sal Khan.
An investment firm creates a graph showing the performance of a specific stock over 12 months. Over the course of the year, is the price of the stock rising, falling, or staying the same? So over this axis right over here, the horizontal axis, they have month by month. And we move forward in time-- July, August, September, October. And in this axis, the vertical axis, we have the price. So, for example, in July the price of this stock was a little over $10. Then in August, it moved up to-- it looks like around $11. And then we could keep going month by month. And this type of graph right over here is called a line graph because you have the data points for each month. And then we connected them with a line. And the reason why we connect them with a line is to really see if there's some kind of a trend here to really show that you have something that's moving from one price to another. And so line graphs tend to be used when you have something that's changing over time. Now, with that out of the way, let's actually answer their question. Over the course of the year, is the price of the stock rising, falling, or staying the same? So on a month-to-month basis, you have, for example, from July to August, the price went up. Then from August to September, the price went down. Then it went up for two months. Then it went down for a month. Then it went up for a couple more months. Then it went really up from February to March, went all the way up to almost $17. Then it went down again. And then it kept going up again. But they're asking us not did it go up every month. They're saying over the course of the year is the price of the stock rising, falling, or staying the same? And if you go from July, which is where our data starts right over here, our price was around $10. And even though there were a few months where it went down, the overall trend is that the price is going up. The overall trend is that the price going up. And you can even see that. In July, it was $10. And then by June of the next year, it was approaching-- I don't know, it looks like it's about a little over $16, maybe almost $17. So it actually had gone up a lot. They don't give us July of the next year. But the overall trend is definitely the upwards direction right over here. And you can see it just visually by looking at this line graph. Even though there's a few bumps that go down, the overall direction is upward.