Boterham (comes from boter -> butter and ham -> ham) is a more traditional way of saying, a slice of bread. 'Boterham met Kaas' is a slice of bread with cheese. Although there are discussions online arguing boterham can also mean the whole package, like with a topping and perhaps even two slices of bread. Broodje is a bun, like the ones you use for a hotdog. Sneetje (the word comes from snijden - cutting) is also a slice of bread. 'Sneetje' maybe more often used when the number of slices are used in the conversation. This for sure is only the slice of bread without any topping.

It depends on the place you are a bit but this should work most of the time ‘Een broodje’ this is like something bread a like. This could be a sandwich, panini, a bun etc. Its most of the times used when its more than just the bread. Its bread with something on or in it. ‘Boterham’ this is a slice of a whole bread. So you would ask would you like this on a boterham or a wrap. ‘Een sneetje brood’ is the same as a boterham. Its 1 slice of a whole bread. Its not just that much and i prefer to use boterham in most situations. Hope this helps