To find out more you can click the link to the forum or click on your "Notifications" in your inbox to read this message:
So basically, ROBLOX are making some security improvements for people's accounts, which means you must verify your e-mail. To try to persuade people to do this, they will give players with a verified e-mail address a free hat, seen below.
Strange that it says the hat was created in 2012, it must have just never been released.
The notification explains how you check if your e-mail address is verified, it is very easy to do and takes under a minute, so it's worth doing. In my opinion, ROBLOX should just make people verify their e-mail as soon as they make their account.
The hat will be given out on November 17th. I am not sure why it says "Get Gear No One Else Has" when the item you get is a "hat", and almost everyone on ROBLOX will have it as most people will have verified their e-mail addresses. So the ROBLOX notification is not really true.
Anyway, I hope this helps you. Thanks for reading!
-Bobstar500