Punctuality means you get somewhere on time or do something on time. Punctuality is important so you can show respect and so you can learn what you need to pass a test or something.

I get to Demo practice on time because it shows respect to Master B. S. Lee and my teammates. If I'm late, my teammates will have to review what they already know because I don't know what they do. Also, Master B. S. Lee might feel angry because he would have to review the whole thing over again with everyone. Another reason I get to Demo practice on time is so I can learn what I need to for a performance or tournament.
I get to school on time so I can learn everything I need to. If I'm late to school, I might miss some learning time. Also, I might miss something I enjoy, for example PE.
I turn in my homework on time so when its time to test I know what to do and so I don't get yelled at. I also turn it in on time so the teacher can advise me so I know what to fix.
This is how I show punctuality in my life.