Now I have an 8 year old daughter who likes to read everything.

A few days ago, she was browsing through my phone and came across the word 'Sexual', and then she asked 'Daddy what is Sexual?

The question was so unexpected and I just mumbled something but couldn't exactly answer the question. I have been thinking without actually coming up with an appropriate answer

Now I need help. What should I be answering?

sometimes kids are empty vessels can you feed sny information you like just like things like tooth fairy, santa etc

so with your child use the same idea, eg sexual you can say are things for adult married people