Okay kiddo, ghaflah is a big word that means forgetting or ignoring important things that we should be remembering.
For example, when we have an important test coming up but we spend all our time playing video games instead of studying, that's ghaflah because we forgot that our education is important and ignored the need to prepare for the test.
Or when we know we should be kind to others but instead we say mean things, that's ghaflah because we forgot to be kind and ignored our responsibility to treat others with respect.
So ghaflah means forgetting important things and not taking care of our responsibilities. It's important to avoid ghaflah and always remember what's important in life.