JAMstack stands for JavaScript, APIs, and Markup. The term was coined by Mathias Biilmann to describe a modern web development architecture based on client-side JavaScript, reusable APIs, and prebuilt Markup.
The static nature of a JAMstack app makes scaling easy, and causes little to no dev-ops overhead. The JAMstack approach can also improve your app's security posture since static sites generally have a small attack vector.
Another benefit is a lot of functionality that was traditionally processed in the back-end, now takes place in the user's browser. And the fact that the stack is JavaScript-based is a great bonus for web developers.