Financial accounting produces the standardised statements, income statements, balance sheets, that a company reports outward to investors, lenders and regulators, following externally imposed reporting rules designed to let outsiders compare different companies on roughly equal terms. Cost and managerial accounting is a genuinely different practice, producing detailed internal reports meant purely for a company's own managers to actually make operating decisions with, and these internal reports never have to follow the same external reporting standards, or even be shown to anyone outside the company at all.
Financial accounting answers a question outsiders are asking
Financial accounting exists to answer a specific outward-facing question: how is this company actually performing, presented in a standardised format that lets an outside investor or lender compare it fairly against other companies using shared accounting rules everyone involved has agreed to follow. Because it's built for outside consumption, financial accounting reports at a relatively high level, a company's overall revenue and expenses, without necessarily breaking down exactly which specific product, department or process actually drove those numbers.
Managerial accounting answers questions only the company itself needs answered
Cost and managerial accounting instead exists to answer internal operating questions financial accounting's high-level, externally standardised reports were never built to address: exactly how much does it cost to produce one specific unit of a particular product, which specific product line is actually most profitable once every relevant cost is properly allocated to it, and how would a specific proposed operational change actually affect the company's internal costs. Because these reports exist purely to help internal managers make better operating decisions, they can be built in whatever level of detail and whatever specific format is actually useful internally, entirely unconstrained by the external standardisation financial accounting requires.
What we're still unsure about
The basic distinction between financial accounting's external, standardised reporting and managerial accounting's internal, decision-focused reporting is well established, foundational accounting practice, taught consistently across accounting education. What's more genuinely a matter of ongoing practical variation is exactly how different companies actually choose to allocate shared, indirect costs across their different products or departments for internal managerial purposes, since several defensible cost-allocation methods exist and none is externally mandated the way financial accounting rules are — companies and cost accountants continue to make real, sometimes contested judgement calls about which allocation approach most accurately reflects their own specific operations, rather than there being one single correct method that applies universally.
This sits inside Cost Accounting & Managerial Accounting, one of seven topics in Accounting, one of four domains in Business, one of seventeen subjects the app can quiz you on.