I want to better understand the difference between the 1-month and 3-month SOFR rate, and when to use each for cash flow discounting.

For example - I have a 5 year project, and someone has decided to use the 3-month SOFR rate. My question is why? What does this assume about the movement of cash flows?

Furthermore, I would like to know if there is a mathematical relationship between two (1-month vs 3-month)

Any useful web links are appreciated.

Thank you very much