The invitation link is used for the first registration in the PlayerPlus app. You can send this to the new members in the team and with one click on the link, they are directly in the right team and can register with an email address and a password.
For security reasons, the invitation link is always valid for 14 days and can be regenerated by the coach at any time. How to do that you can read here.
IMPORTANT: The invitation link does not serve as a login in, but is only suitable for the initial registration.
IMPORTANT: If you already have a login from SpielerPlus, you can use it again for a new team. The logins will be merged automatically, so that you have both teams in your overview.