1. What is the difference between a histogram and a bar graph?

They are both similar but there is an important difference.

histogram is used for continuous data such as measurements and the bars are joined together.
bar graph is used for discrete data which can be counted and the bars can be drawn not touching.

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.

4. What is the difference between continuous data and discrete data?

CONTINUOUS data is usually the result of measurement.

e.g. The heights of people.

DISCRETE data is usually the result of a counting process.

e.g. The number of people at a game of cricket.

5. Does TIME always have to go on the horizontal axes of a time series graph?

Yes, time is always on the horizontal axes.