Lay vs. Lie: The Most Confusing Verb Pair

Lay is transitive, it takes an object. You lay the book on the table. Present: lay. Past: laid.

Lie is intransitive, no object. You lie on the couch. Present: lie. Past: lay. (Yes, the past tense of lie is lay. English is cruel.)

Past tense recap: lay → laid ("I laid the keys down"). lie → lay ("I lay on the couch yesterday"). lie (untruth) → lied.

Most people say "I'm going to lay down" when they mean lie down. It's wrong but so common that fighting it in casual speech is probably a lost cause.