In cooking, what is the difference between breadcrumbs and crumble?

Ansence of Oats

Breadcrumbs are just that - bread that has been shredded or grated to produce small crumbs. As a topping (say, on a tuna casserole), the breadcrumbs are mixed with melted butter and sprinkled on the top. Crumble, on the other hand, is a topping produced by mixing flour and other ingredients - usually oats and sugar of some type - before adding butter to the mixture before baking it on top of the dish. Here's one crumble topping:

To make the apple crumble topping, put flour, oats, coconut and brown sugar into a large bowl. Drizzle over butter and stir until just combined into a lumpy mixture.

https://www.bhg.com.au/classic-apple-crumble