why am I getting text messages stating someone accessed my account

Review if any devices are logged into your account by going to Settings > [name on top], and scroll to the bottom to view who is logged in. Out of an abundance of caution you can also change your Apple ID Password.

Apple does provide an email if that occurs, but not a text message. I would view this as a phishing scam trying to get you to give the scammer your Apple ID and Password. With that information the scammer can lock you out of your device.

Review this document to identify and report phishing scams:

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

Who are the emails from? What is the exact text of the email?

You will get an email from Apple any time someone logs in to your Apple ID, and from some other providers when someone logs in to your account, such as gmail or Microsoft. If you know who logged in or it was you it is safe to ignore it.

If it wasn’t you, DO NOT CLICK ANYTHING IN THE EMAIL, as it could be a criminal out to steal your data or money→Avoid phishing emails, fake ‘virus‘ alerts, phony support calls, and other scams

What account? If you think your Apple ID account was compromised, change your password.