Trash culture is a term used to describe things that are not very good or valuable, and are usually thrown away or forgotten about. Imagine if you had a toy that was broken and you didn't want to play with it anymore, so you threw it away. That toy could be called "trash."
Now, imagine if lots of people started to like things that were like that broken toy - things that weren't very good or valuable. Those things could include bad TV shows, cheap clothes that fall apart after one wash, and fast food that isn't good for your body.
When lots of people like these kinds of things, it can be called "trash culture" because it seems like people are valuing things that aren't very good or meaningful. It's like they're filling up their lives with stuff that isn't worth much, and not really thinking about what is truly important or worthwhile.
So, overall trash culture is when lots of people value things that aren't very good or meaningful, and they fill their lives with these things instead of focusing on more important or valuable things.