You are seeing a graph plotted on dashboard of Google analytics. You can change the graph report for visits, page views, bounce rate, Avg. Time on Site, %New Visits etc. Just you will have to click on the tab to drop down the option menu to view the graph which you want. Let see the image below, a red box marked in image, where drop-down tab is available to plot different graph.
By default the graph plotted for visits. After selection of any option, graph will automatically plotted. Graph plotted datewise by default for a month only. If you put mouse cursor on graph, the date range appears automatic which tell us the record for particular date. Let see the below image.
The graph describe clearly how the traffic acting on your site. You can have an idea to make your next target or plan after tracking the traffic and visit, page views, bounce rate etc by Google Analytics Graph.