What is the difference in application between a bar chart and a pie chart?

1.   What is the difference in application between a bar chart and a pie chart?

2.   What is the difference between a frequency distribution and a cumulative frequency distribution?

3.   In a bar chart, why are there spaces between the bars on the horizontal axis?

4.   The following frequency distribution shows the distribution of delivery times (in days) for swimstuff.com customer orders during the last month