A good newbie question.
This is due to that some repositories are unauthenticated. As long as you only use the ones included from the beginning, and some that you may have been encouraged to add in an answer (at least by the senior members) in this forum you are safe.
It's a bit like when you get a warning in Windows that a driver is not certified by Microsoft
updates available unauthenticated! May allow malicious user
Forum rules
Do not post support questions here. Before you post read the forum rules. Topics in this forum are automatically closed 6 months after creation.
Do not post support questions here. Before you post read the forum rules. Topics in this forum are automatically closed 6 months after creation.