Distribution describes how data is distributed throughout a graph.
Normal distribution is a pattern in data. It is when the data is distributed around the average regularly, which when plotted as a histogram will result in a bell curve. In a Gaussian distribution, data tends towards the mean which means that the closer a value is to the mean, the more regularly it will appear. Essentially, Gaussian distribution is based on a 'bell curve'. Thus, in this "normal" distribution, the top of the bell is obviously the mean.
In statistics, a bimodal distribution is type of distribution with two different modes. These are two different and distant peaks, and in these cases, generally, there are two "bell shapes". An example of this would be for finding the mean of a test. If a lot of people got a high test result, and yet a lot of people got a low test result, then the average would be between them, even though very little people probably got the average.