Difference between ‘lie’ and ‘lay’ and ‘laid’?

Before we get into the really confusing aspects of lay, lie and laid, let’s put aside another meaning of lie – to say something untrue.

The verb lie used in the sense of speaking something untrue has its past and past participle forms are lied and lied.

So, when you say something which is not true, you lie. Examples:
1) Why did you lie to me when you knew the doctor will not come.
2) He is lying. His father was a constable not a judge.

Now, lets come to the more complicated meanings:
Lay – to put someone or something horizontal in a rest state.

Examples:
1) Sudhir laid the mat in the balcony.
2) Please lay the bricks in the open space near the well.

Lie means to make yourself horizontal (or, to lay yourself).
Examples:
1) Why do you lie the hole day in such a dirty bed.
2) Sudhir was lying under during the earthquake.

So, lay is used when a subject lays something else, lie is used when the subject lays himself.