A histogram is a graphical representation of data. It shows the distribution of values within a set of data. The bars represent the number of observations at each value.

Bar charts are similar to histograms but instead of showing the frequency of observations, they show the probability of a discrete observation occurring.

Histograms and Bar charts are used to analyze data and determine if there are any outliers or unusual patterns. They can also be used to compare two sets of data.

**Use Case for Histogram**

Histograms are often used to compare the distribution of data between two groups. For example, if you were comparing the marks obtained by students in two subjects, you could use a histogram to see if there was a difference in the distribution of marks between the two subjects.

You can also use a histogram to compare the distribution of values within one group. For example, you might want to see if the distribution of heights in a classroom is normal or skewed.

**Use Case for Bar Charts**

A bar chart is a type of graph that shows data in a way that makes it easier to compare discrete data. It's also called a "bar" chart because each quantity is represented by a vertical line.

Bar charts are used to display information in a simple and clear manner. For example, if you want to see how much money you spend on various expense groups (e.g. food, rent, entertainment etc) you could use a bar chart to compare these categories.

**Visual Difference between Histogram and Bar Charts**

The main visual differences between a histogram and a bar chart are:

1. In a Histogram there is no gap between bars, while the Bar Chart has space between bars. Most of the time, this rule holds true. However, Histograms created by Microsoft Excel have space between two bars.

2. In a histogram, the height represents the count/frequency for a range of values (called bin or class), whereas in a bar chart, the length of the bar indicates the count for a specific category.

3. A Histogram shows the frequency distribution of continuous variables, while the Bar Chart shows the distribution of discrete variables.

In summary, both types of graphs provide different ways of representing data. A good understanding of their uses will help you choose which kind of graph would best suit your needs.