S4H Scrap for hire. This is when someone makes layouts/pages for books for a person and is paid for it. So you are hiring someone to scrap for you.
S4O Scrap for others - basically another name for S4H and could be paid or unpaid.
PU is personal use. You may usually only use these for your own personal use and not share them with anyone.
CU is for commercial use. Generally it means you can use for making scrapbook kits and you need to read each designers terms of use to see the details of what they allow for commercial use.
