New Employee
The first few weeks on a job are usually defined by one thing: everything is new. That is essentially what the term describes, someone who has just joined an organization and is still finding their footing in a role, a team, and often an entirely new set of systems and processes.
During this stretch, most of the attention goes toward getting that person up to speed: introducing them to how the company actually works day to day, running them through the training they need, and helping them settle into their responsibilities without feeling thrown in at the deep end.