When writing, I usually get confused between when to use "Let's" and "Lets". Do I use let's in place of "let us", and lets everywhere else?

"Lets" means "does let".
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So, would this be correct? I've been wondering the usage of this for quite awhile until I remembered this site:

"Let's go to the store".

As in, "Let us go to the store".

Can I have an example of when "Lets" would be used in a sentence?
Every night he wants to go out, and she lets him.

Having lots of money lets you do lots of things.

Can I use Lets in an imperative mode?

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