Well, folks, this is a toughy for most people, so don’t be discouraged if it takes you awhile to understand it. But do not give up! With practice you will get it right.
In difficult grammatical terms, to lay is a transitive verb and, as such, takes an object. It means to place or to set. You lay something, (or crudely someone.)
In simple terms, that means that this verb will commonly be described and followed by nouns or pronouns — words like the book, my head, the new carpet, or crudely, his girlfriend or her.
Audrey is going to lay the new carpet today.
She is laying the carpet in the living room right now.
Yesterday Audrey quickly laid the carpet in the den.
She has laid carpet all week.
In difficult grammatical terms, to lie is an intransitive verb and, as such, does not take an object. It means to assume a position, generally a horizontal one. You simply lie or lie down. Likewise, the carpet simply lies on the floor. Your head simply lies on the pillow all night.
In simple terms, that means that you cannot follow it immediately in a sentence with a noun or pronoun — words like those above that describe what or who (whom.)
That is because, with to lie, what follows the verb applies to the subject of the sentence. As such, it can only be followed by words that describe where, when, why and how the object behaves.
Audrey is going to lie down on her bed when she finishes dinner.
She was lying down for a long time before dinner too.
Yesterday Audrey lay down all afternoon.
She has lain down exhausted for several hours every day this week.
Please feel free to fill in the missing verbs in the sentences below. I will be happy to correct them for you.
Or ask me to clarify my explanations. Perhaps I have missed something.
1. The snow __________ softly under the trees last night.
2. The young girl _________ her dolly in her bed last night.
3. He _______________ the document in front of me right now.
4. The master told his dog to _____________ down.
5. He said, “____________ down.”
6. The dog __________ in the same position for several hours.
7. Before then he _______________ outside on the porch for a long time.
Good luck, and maybe you would like to send best wishes to Audrey for all her hard work with the carpeting.