An application is initiated by the specialist. They find the vacancy, read the terms, and submit an application. This means the specialist has already expressed interest in your vacancy.

An invitation is initiated by the company. The company finds the specialist's CV and offers them a vacancy. In this case, the specialist still needs to decide if the offer is interesting to them. They can accept the invitation by clicking apply or decline it.

Both scenarios are necessary. Applications help receive incoming interest from people who are already looking for work. Invitations help the company actively seek out suitable specialists, especially if waiting for applications is not enough.