Brokered CDs with 5% interest? Can someone ELI5? – I’m just finding out about these now and not quite sure I am doing the right thing. Any specific advice /be aware of?

As subject says, just saw there are Brokered CDs with up 5% interest. Looking at Vanguard now and thought I might try buying one of the 4 month ones for 4.5% to try it out, but want to make sure for those have done so if there is anything specific you wished you would have known (fees for purchase, type, etc) before doing so…

Thanks for any insights!