Zero trust is built on the idea that being inside the office network, or logged in once, should not automatically grant access to everything. Each request is checked: who is asking, from which device, and whether they are allowed to see this particular thing.
In practice it means strong sign-in checks such as MFA, access limited to what a role needs, and ongoing monitoring. It suits businesses with several sites, remote staff and cloud systems, where the old idea of a secure perimeter no longer holds. It is a way of working, not a single product you can buy.