This is the first in a series of quick grammar lessons. These are little things that I come across every day as an English teacher. Each of these topics could be explained at greater length and in more detail, but the point here is to address the basics and provide a quick, useful takeaway. So here's installment number one: lie vs. lay.
To lie is to recline. As in, "I want to lie down after work."
To lay is to put or place. As in, "Please lay your applications on my desk."
The tricky thing is that the past tense of lie (to recline) is lay. As in, "This morning I lay in bed for an extra ten minutes." or "She had lain there for a long time before she realized what time it was."
The past tense of lay (to put) is laid. "Yesterday, the crew laid new concrete on the front steps."