A pie chart is a circular graph that shows the relative contributions of different segments. This is mostly used while representing percentages from various categories.
For example, you can use a pie chart to show revenue contribution from different territories or percentage of leads from various campaigns.
A line graph connects individual data points over a specified period to show a rise or fall in numbers. It compares the changes over a short or long time period and is useful in identifying market trends.
You can use a line graph to represent raising or falling sales numbers, customer churn rate, or website traffic over a specific period.
Bar charts are used to compare the metrics between different categories over a period of time. You can use a bar chart to show the sales for different products in your company or revenue from different sources.