Final answer:
A line chart with no axes that shows trends in time series data is called a sparkline. Sparklines provide a quick overview of data trends without detailed context.
Step-by-step explanation:
A line chart that has no axes but is used to provide information on overall trends for time series data is called a sparkline. Sparklines are compact, inline charts that show trends in a series of values without the typical layout of axes found in more elaborate charts.
They are useful for providing a quick glance at the trend or pattern of data over time, without the more detailed and scaled context a full chart provides. One common line graph is a time series, which usually has axes showing the progression of time on the horizontal axis and another variable on the vertical axis. This format is often the most effective for illustrating relationships between two variables that are changing, such as the unemployment rate over time.