Nature abhors a vacuum. Cathy is right in that the saying relates to physics. . More importantly, it is a metaphor. It is widely applicable to many different areas. It is saying that things in life do not tend to exist in isolation, emptiness. People tend to not have empty spaces, time, lives. If someone stops doing their hobbies, they tend to start doing something else. Their world does not tend to stay empty for long. If you cancel your lunch-time class & have a free hour, you will likely find something else to do in that time. A rearrangement in a shop, might leave a space: It will be filled. . An empty piece of land, tends to be discovered & used by someone. . A very general concept & metaphor. Lives tend to be full, or at least, not empty. . There was a gap here, with no answer explaining the metaphor. You know nature abhors a vacuum, so someone was going to come & put something here.

"Vacuum" here is not the cleaning tool, but rather a vacuum in the sense of physics - basically a space that is completely empty of all matter. "Nature abhors (hates/dislikes) vacuums" because none exist in the natural world.