Question about background check

From what I understood, background check comes later in the process. and USCIS will do the background checks themselves during or after the biometrics and fingerprints.

but someone told me today that we had to go somewhere to get our backgrounds checked and send the notarized paper with the application. the problem is i already sent my application and everything without this. does anyone know anything about this? or is it a complete bs?

complete bullshit, unless you suspect you did something and you didn't know.

They will background check us.

I had the same question today. Anyone have an official answer???

This is the answer.

They need to do biometrics and fingerprinting for our background check.
Maybe your friend misunderstood since you need to provide documents in your application if you were arrested or charged for something.