Business Email Compromise is when fraudsters send an email message to companies or individuals that appears to have come from a known source (associate / vendor / supplier). The email may seem to be about legitimate request to change beneficiary bank account details for regular / future money transfers or payments.
Fraudsters communicate with the victim through compromised/look alike spoofed email account or website. They use slight variations on legitimate addresses (for example, Mohamed@companyABC.com vs. Mohammed@CompanyABC.com) in order to fool victims into thinking that the fake accounts are authentic.