Vertical lines have equations of the form \(x = k\). Horizontal lines have equations of the form \(y = c\). Draw the graph of \(x = 3\). Mark some points on a grid which have an \(x\)-coordinate ...

There is a title which tells you what the data in the time graph is about. The horizontal (X) and vertical (Y) axes or lines are labelled to tell you what data has been collected and when.