It’s a good amount of work for a questionable practice but man, oh man, do we appreciate bread when we’re done!
All these things are called chametz.
I had a friend whose family actually hunted for chametz with a feather and a wooden spoon to sweep it into, the traditional way to approach getting ready.
We don’t go quite so far, but I like what our Haggadah (the book that directs the Seder) has to say about the last of the chametz:
“Do you think we found every last crumb? Probably not. After all, we’re not perfect; we’re human. Here’s a prayer we can say together about any crumbs we missed:
If there are any crumbs I haven’t seen or taken away, I hereby disown them. I declare them to be nothing – as ownerless as the dust of the earth.
No one can be perfect. We can never get rid of every crumb or stop making mistakes. All we can do is try. Searching for chametz is a way of trying.”