Okay, so imagine you have a toy that you really like to play with, but you're not sure if it's the best toy ever. You might ask your friend if they have a toy that's even better than yours. Your friend might say "Yes, I do have a better toy, but it's not as good as it seems. It's sometimes hard to play and sometimes breaks easily."
That's kind of like what evidence lower bound means. When scientists are doing experiments, they want to make sure that the evidence they're getting is good enough to support their ideas. The evidence lower bound is like a toy that they're trying to compare their experiments to. The lower bound is the minimum level of evidence that they need to show that their experiment is good enough.
The lower bound is important because it helps scientists figure out if their results are really meaningful. Just like how you wouldn't want to get a toy that's not very good, scientists don't want to get data that isn't good enough to support their ideas. The evidence lower bound helps them know when they've got a solid enough foundation to make their conclusions.