On the first page of the Chart Wizard you can choose a chart type.
A line chart shows values as points on the y axis. The x axis shows categories. The y values of each data series can be connected by a line.
Points only - this subtype plots only points.
Points and lines - this subtype plots points and connects points of the same data series by a line.
Lines only - this subtype plots only lines.
3D lines - this subtype connects points of the same data series by a 3D line.
Mark Stack series to arrange the points' y values cumulative above each other. The y values no longer represent absolute values, except for the first column which is drawn at the bottom of the stacked points. If you select Percent, the y values are scaled as percentage of the category total.
Choose the Line type from the dropdown to select how the points will be connected. You can choose either Straight lines, Smooth lines to draw curves through the points or Stepped lines to draw lines which step from point to point. Click Properties to change the properties for the smooth or stepped lines.