HTML naming, breaking any rules in google?

[---Genetic---]

Hello all just wondering if I'm allowed to do this because I have been thinking of doing it, for example say if I typed in ''weight loss'' in google, google would then search for anything containing those words and will prioritise this by url as well as header and description. I was thinking of duplicating my home page which is a one page sales letter website and call it a different name for example www.example.com/weightloss.html

but that would be the same page as www.example.com

am I allowed to do this?

sorry if it seems confusing hard to type what i'm thinking
give it 5 mins and then reply