Help Me Understand: Romance vs. Spice vs. Smut in Fantasy Books

Please someone help my dumb male brain spot the difference. I'm new to the genre (On my 3rd book) and I know romance is pretty easy to spot but I don't understand what would make something "Spicy" versus Smut. Help me out I'm trying to relay the differences to my other male reader friends who view these books as "Chick Books". I've read Five Broken Blades, Four Ruined Realms and now Fourth Wing. where there has been romance there's also been some explicit scenes. That doesn't always translate to spicy or smut.