A regular application starts with you. You found a job opening, decided it suited you, and sent an application to the company.

An invitation starts with the company. The employer found your CV and decided to offer you the position. You are no longer looking for this position yourself, but you can consider the offer.

In both cases, a connection is established between you and the company. The only difference is who took the first step. An application shows your interest; an invitation shows the company's interest.