what do you name your subdomains? need examples

If you're going to have a few, use a Domain property in Search Console rather than a URL-prefix one. It covers every subdomain under one roof, otherwise you end up verifying each one separately and forgetting half of them.

short and by function, so anyone can guess what's on it: app. for the product/login help. or support. for docs status. for uptime shop. if the store is a separate platform staging. or dev. for testing (password protect it or noindex it, staging copies getting indexed is a classic) I'd keep the blog in a /blog folder rather than a subdomain if you can, but that's a whole debate. what's it for?