answered question
Sex is when...well it's complicated but if it's "right" a man passes on his sperm to the female and one of the females eggs sometimes takes in the sperm to create a human being. That's the basic meaning of what it is...
To have knowledge. Even if you don't have a job or career that will use the complex formulas and stuff, basic knowledge. If you have children and they need help with homework you'll be able to help them. It would be a little embarrassing if you aren't able to help