Layed and laid are two words that can often be confused with one another. Not only do they sound the same, but they have the same meaning. They are both the past tense of the word lay. It is referring to the action of laying something down.
The difference is that the word layed is no longer used. It was once the most common word used, but because of English rules, it is not acceptable for a word that ends with a y, has the past tense word end with ed. Now, the past tense of the word that is accepted is laid.