A statute of limitations is a law which sets the maximum time period within which certain legal actions can be brought forward. After the expiration of this time, the claim under consideration is deemed invalid.
To put it simply, let’s say you tripped and fell because of a broken sidewalk and you got hurt. You decide you want to sue the city for not maintaining the sidewalk properly. However, you can’t wait forever to file this lawsuit. The law gives you a certain time limit to do this (for example, 2 years). If you don’t sue within that time (2 years), you lose your chance to sue. This time limit is what we call ‘the statute of limitations’.