Alright kiddo, imagine you are walking on the floor with your shoes. When you take a step, your foot pushes on the floor and the floor pushes back on your foot with a force so that you can move forward without slipping.
Now, let's say you are walking on a very slippery surface like ice, your shoes won't have enough grip to push back on the floor hard enough, so your foot will slide and you may fall down.
The slip factor is like a measure of how much your shoes can grip the floor. If the slip factor is low, it means your shoes are not very good at staying in place and you may slip and fall. But if the slip factor is high, it means your shoes can grip the floor really well and you can walk without slipping.
So basically, slip factor is a way of measuring how easy it is for your shoes to slide or slip on different surfaces. The higher the slip factor, the less likely you are to slip or fall down.