1. What is the difference between a column graph and a bar graph

They are both the same.

histogram is used for continuous data such as measurments and the bars are joined together.

2. Can a pie graph be used for all types of data?

No. Pie graphs or charts are most suitable to data where proportions or percentages of a total amount are available .

3. How can the pictures in pictographs show numbers?

Each picture represents a certain number of items.