IP Whitelist is a list of IPs that are allowed to use the package. This is a kind of list of invitees:
if it is empty - everyone can use the package with login/password authorization;
if an IP is whitelisted, only the included IP can use it.
You need to put your IP into the Whitelist if you use IP authorization.
More about login/password authorization and IP authorization.
Remember, if your IP Whitelist is empty - everyone to whom you have ever provided its data will be able to use your package.
Here is a short tutorial regarding IP Whitelist setup: