A line chart or line graph is a type of chart which displays information as a series of data points called ‘markers’ connected by straight line segments. It is a basic type of  chart common in

many fields. It is similar to a scatter plot except that the measurement points are ordered (typically by their x-axis value) and joined with straight line segments. A line chart is often used to

visualize a trend in data over intervals of time – a time series – thus the line is often drawn chronologically. In these cases they are known as run charts. [wiki]

Line chart with one group


Line chart with several groups


Bad chart