Total addressable market
Also known as: TAM
Total addressable market (TAM) is the opportunity available to a company if it captured every customer who could realistically buy what it sells, across every market it competes in. It's a ceiling, not a forecast, no real company captures its entire TAM, but it sets the scale of what's actually possible before competition, cost, or execution take their share.
TAM matters most when judging how much room a company has left to grow. A business with a high share of a small TAM has less room to keep compounding than a business with a smaller share of a much larger one, even if the second business's current numbers look less impressive today. Entering a new, related market expands a company's TAM, but a bigger addressable market on paper doesn't guarantee a bigger business, the company still has to actually win share inside it.