Remember we set up our permalinks to be Category/Post Name? The slug is by default the post name. However, post names often contain stop words such as a, an, the, etc. that just dilute the effectiveness of the main words in the title. You'll want to either manually strip those out, or use a plugin to do that automatically for you.
So for example, if the title of your cake recipe is A Cherry-Filled Chocolate Cake Recipe With Walnuts, you'd want to change the slug to ”cherry-filled-chocolate-cake-recipe-walnuts”, deleting ”a” and ”with” from the slug.