Lie (to fib): lie > lied > lied
Lay (to set down): lay > laid > laid
Lie (to recline): lie > lay > lain
The first (to fib) is a simple verb; the second (to set down) is a transitive verb—it conveys an action from subject to direct object; the third (to recline) is another simple verb. Thus The prophet lies, She laid the book on the table, and He has lain there for hours.