CLNs sometimes get confused with SAFEs as they are both agreements you make with investors that help you raise money before a funding round.
The main difference between SAFEs and CLNs is that convertible notes are debt-equity (also known as quasi-equity) instruments while SAFEs are equity agreements. The convertible debt can be repaid in certain scenarios, and it can carry interest, while a SAFE (such as a SeedSAFE or a SeedFAST) is not repayable at all.