How secure is iMessage?

This “linkage” allows you to FaceTime and iMessage to/from your laptop …

… while using the single iPhone phone number as your “address.”

As previously posted, iMessage is VERY secure.

If you’re interested in a “deeper dive” on the subject, this document is a good place to begin:

iMessage security overview – Apple Support (AU)

By design, Apple wants to link everything ... all devices and pretty much every app that allows it. You allow it when you establish your Apple credentials; your Apple ID. Some things you can opt out of or turn off.

As to security, it's as secure as the Apple ecosystem in general. Nothing is perfect, but Apple does make periodic security updates to counter known threats.

Re: “… need to become more informed about the technology I use in my daily life rather than just passively using … “

You should not only “protect” youself … but think thru - and practice - EXACTLY what you need to do if your phone is damaged, lost, or stolen. When you NEED to do it is NOT the time to learn.

Apple def provides all the tools; one just needs to use them. Here’s a good primer:

Use the built-in security and privacy protections of iPhone – Apple Support (AU)

Apple offers end-to-end encryption for a secure connection. 