SaaS (software as a service) is a model in which software runs in the cloud and is paid for by subscription, with users accessing it through a browser – no installation, servers or maintenance of their own.
For the customer, SaaS means convenience: always the current version, access from any device, a predictable monthly cost. For the maker, it is a business model: one product serves many customers and revenue is recurring (hence the key metrics MRR, churn, LTV).
Building a SaaS product is more than building an app: you need accounts and permissions, subscription billing, user onboarding, and the security of many companies' data on shared infrastructure (multi-tenancy).
For service companies SaaS is often a natural evolution: a tool built for internal needs – as in our anonymised case study – becomes a product for the whole industry.