can you tell me what ACCEPTED on my Filed Federal Tax Return mean?

The IRS computers didn’t find any anomalies in your return to prevent processing. 

Accepted does not mean Approved.  And the date Turbo Tax gives you is just an estimated date of 21 days.

Accepted only means the IRS verified some basic info on it so they know it's really from you.  After it is Accepted the IRS processes it then approves it before they send the refund.

After Turbo Tax sends your return they are done with their part.  Now it's up to the IRS to process and Approve it.  It has nothing to do with Turbo Tax.  The IRS doesn't update Turbo Tax with the status of your return.  Turbo Tax just gives you an estimated date.

What does Accepted mean

https://ttlc.intuit.com/community/return-status/help/what-does-accepted-mean/01/26285

IRS Where's my refund

https://www.irs.gov/refunds/