Internal mobility covers vertical moves such as promotion, sideways moves into a different team or function, and redeployment when a role is closing. Many organisations advertise vacancies internally first, or run an internal talent marketplace where staff can see open roles and short projects. A customer service lead moving into a training role, or an engineer transferring to a product team, are typical examples.
Hiring from within can shorten ramp-up time, since the person already knows the systems and culture, and it gives staff a visible reason to stay. The risk is informal selection, where managers tap people they already know. Assessing internal applicants against the same job-relevant criteria as external ones keeps the process fair and makes it easier to explain each outcome.