When you create an Apple ID, you have to enter an email address, and it’s not possible to change it to something different afterwards. The only countries allowed to use something different (phone number) are India and China (mainland).
You need the email address, because Apple will contact you regularly per email, telling you about new apps, features, updates, your subscriptions, ...
You also need it to use the App Store, iTunes Store, FaceTime, iMessages, ...
Whether or not this email address is secure, depends on your settings, als well as your “behaviour”.
With Two Factor Authentication, it’s at least as secure as other email addresses with similar features. Here’s more information:
Two-factor authentication for Apple ID
In addition, you get advice from Apple to keep your ID as secure as possible:
Security and your Apple ID
Recognize and avoid phishing messages, phony support calls, and other scams
There are regular attempts by scammers to take over Apple IDs. A few of our members have reported some of these on iPad Forums. If you fall for this scam, you will certainly weaken the security of your ID.
If you think someone has your login credentials, it might still be possible to regain control:
If you think your Apple ID has been compromised
