BMW M is the performance line, and the letter is the point

M stands for motorsport. BMW M is the company's performance arm, not a trim invented by a dealer. The cars people mean, when they say the letter with any respect, are the M3 and the M5: a 3 Series and a 5 Series developed further by that workshop, with more power and a different brief.

Not every M badge is the same claim

BMW has also used M as a milder mark on cars that are not full M cars. The desk will not treat those as the same thing. If we write M3 or M5, we mean the motorsport car. If a car only borrows the letter, we will say that it borrows the letter.

What M is known for is a driver's car with a usable shape. The M3 in particular became a pattern: a sedan or a coupe you could live with, built harder than the car it started from. That reputation is the fact. A horsepower figure changes every few years, so this piece does not carry one.