The Normal Distribution is one model for continuous random variables that often occurs in practice. Note that not all continuous variables will have a normal distribution - there are hundreds of different distributions. The normal distribution is the most important continuous probability distribution in statistics and is well known to be a good fit in relation to IQ scores. So you could expect in practice to find a little raised bump at the top end of an experimentally gathered set of IQ scores. At the time of writing, I have not seen an explaination for this.
Normal distributions are a family of distributions that have the same general shape.
They are symmetric with scores more concentrated in the middle than in the tails. Normal distributions are sometimes described as bell shaped. Examples of normal distributions are shown below. Notice that they differ in how spread out they are. The area under each curve is the same .