In plain words
An email that looks like it comes from your lawyer, supplier or partner asks for a payment to a new account. No software is broken into; the email is the attack.
Why it matters to a firm
The FBI Internet Crime Complaint Center reports business email compromise among the costliest crimes it records each year. Most cases rely on forged or lookalike email and a payment that is not confirmed by phone.
How anyone can check it
Confirm any change of bank details by phone, on a number you already have, before paying. Then check your own domain’s DMARC record.