Mark H. answered 07/11/19
Tutoring in Math and Science at all levels
"Lay" is normally a transitive verb---meaning that it has a subject and an object. "Laid" is the past tense of Lay.
Example: Please lay your clothes on the bed. OR I laid my clothes on the bed
By contrast, "Lie" is intransitive, meaning that it has no object.
Example: I lie on the bed
Or: He lies
Or: He is lying
Past tense: He was lying, or he lied.
But, you would not say "I lied on the bed"--I think it is correct to say I lay on the bed, and I was lying on the bed.