FBAR and FATCA (which require reports by U.S. persons of interests in foreign accounts) overlap to a large extent. But they impose separate reporting requirements. Failure to comply (especially with regard to FBAR) can have very severe consequences.
FBAR (a foreign bank account report) stems from a banking regulation under the Bank Secrecy Act. It is specifically designed to inform the U.S. government of funds held by U.S. persons in foreign accounts. Since the purpose of this report relates at least in part to the fight against terrorism, penalties for failure to file can be very severe.
FATCA (the Foreign Account Tax Compliance Act) is a tax statute. Pursuant to this federal law, the IRS requires that Form 8938 (Statement of Specified Foreign Financial Assets) be filed annually to report interests by U.S. persons in foreign accounts. This reporting requirement clearly overlaps with the FBAR report. But filing one of them does not excuse filing the other one when required.
Tax preparers are becoming increasingly familiar with these forms. But if you have offshore accounts, you should confirm with your accountant or tax preparer that you are filing all reports that a U.S. person would be required to file to reflect ownership in those accounts.