A tech stack is the group of technologies used together to make and run a digital product. Think of it like the tools and materials used to build a house: each has a different job, and they need to work together.
A website might use one tool to show pages, another to handle requests, a database to remember information, and a hosting service to make the site available online.
There is no single best stack for every project. The right choices depend on what the product needs, what the team can maintain, and how the pieces fit together.