Frequency level refers to how often something happens. Let's say we are talking about how many times you eat ice cream in a week. If you eat ice cream every day, we would say the frequency level of eating ice cream is high. But if you only eat ice cream once a month, we would say the frequency level is low.
Frequency level can also be used to talk about how often something happens in a different way. For example, if you hear your favorite song on the radio every day, we would say the frequency level of hearing that song is high. But if you only hear it once in a while, we would say the frequency level is low.
So, the frequency level basically tells us how often something happens. It can be high if it happens a lot, or low if it happens less frequently.