Total Addressable Market
Total Addressable Market (TAM) is the total revenue opportunity available if a product captured 100% of its target market. SAM (Serviceable Addressable Market) and SOM (Serviceable Obtainable Market) are more realistic subsets investors use to evaluate opportunity size.
Notion's TAM is the global productivity software market (~$50B+). Their SAM is knowledge workers in tech companies. Their SOM is what they can realistically capture in 3–5 years.