lay versus lie

lay - lie
`lay'
Lay is a transitive verb, and it is also a past tense of another verb, lie.

To lay something somewhere means to put it there carefully.
   Take the top sheet and lay it in the centre of the bed.

The other forms of `lay' are lays, laying, laid.
   He lays the negatives in the frame.
   `I couldn't get a taxi,' she said, laying her hand on Nick's sleeve.
   She laid the cigarette in the ash-tray.

`lie' used as a verb
Lie is used as an intransitive verb with two different meanings.

To lie somewhere means to be there in a horizontal position, or to get into that position.
   She would lie on the floor in her overalls.

When lie is used like this, its other forms are lies, lying, lay, lain. The past participle lain is rarely used.
   A dress lies on the floor.
   The baby was lying on the table.
   I lay in bed in the dormitory.

To lie means to say or write something which you know is untrue. When lie is used like this, its other forms are lies, lying, lied.
   Why should he lie to me?
   Rudolph was sure that Thomas was lying.
   He had lied about never going back.

`lie' used as a noun
Lie is also used as a noun. A lie is something that someone says or writes which they know is untrue.
   He knew that all these statements were lies.

You say that someone tells a lie.
   I have never told a lie to my pupils.

You do not say that someone `says' a lie.

Source: Collins Dictionary