Hello there johnyankeedakota,
I understand you've noticed a folder appear on your MacBook that is titled "facebook_files" that you're curious about, right? Let's see if the following information may be helpful.
For starters, let's make sure you're up to date with the latest macOS version. If you see that an update is available, be sure to create a backup of your information prior to installing. If you need assistance with either of these steps, check out the following resources:
Back up your Mac with Time Machine
Update macOS on Mac
Once you confirm that you're up to date with the latest macOS version, let's check to see if you have Facebook added as an internet account on your Mac. For assistance with checking this, take a look at the following resource:
Use your internet accounts on Mac
If you do see that Facebook is added here, do you sync contacts or any information from Facebook that you need? If not, try removing the account to see if this continues. If it does continue, are you aware if you're saving items from Facebook that could be placed in this folder?
If you're unable to determine at this point, Contact Apple Support to look into this with you in more detail.
Have a great day!