Prevalence refers to the number of people who are available at a certain time period. For example, prevalence can refer to the number of people who are experiencing the same thing during the pandemic. The incidence will refer to the rate of people who develop a certain condition.
For example, how many people develop Coronavirus for a certain time period. These two things will measure the number of people, but there are times when they are loosely used, or people are not exactly sure how they can be used. Most of the time, they are expressed with the use of proportion or a rate—the clearer the usage, the more that they will be understood.