How to tell if my Xfinity1 Wifi connection is secure?

I have the triple play package with the Xfinity1 platform. Very recently I discovered that I have Wifi as well. Didn't know that fact till I checked my account online. Nothing was ever mentioned in my paper statements.

Just to clarify, I was not at home when we upgraded our service in 2018. The tech who updated our equipment had obviously set up a username and password for me as well. Otherwise I've been getting internet via ethernet connection to PC.

Now that I have Wifi, which is something new too me. How can I tell if it is secure? Is it private or public? I thought you needed a router to get wifi?

Can anyone tell me please, if my Wifi connection is secure?

Thank you.