What does 7 day yield of 4.27% on a money market fund mean?

Does that mean every 7 days I get 4.27% of my principal? So for example if I put $1000, in 14 days I get $85.4? Or is it 4.27% annually?

Wondering whether I should purchase bond/CD of 3 to 12 months or a money market fund such as SWVXX to park some cash