Someone use my Apple id

I think you are seeing an attempted scam.

Did you provide any potentially damaging information to anyone? If yes, you'll need to follow up, for example, with a credit card company, Apple, your bank, etc.

If you gave you Apple ID password to a scammer, then

Change your Apple ID password https://support.apple.com/en-us/HT201355

Here is What to do [before] or after you change your Apple ID or password https://support.apple.com/en-us/HT204071

See If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145 to see what to do.

Increase the Security of your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

FYI: 

 See If you see apple.com/bill, itunes.com/bill, or an unfamiliar charge on your statement https://support.apple.com/en-us/HT201382

See Identify legitimate emails from the App Store or iTunes Store https://support.apple.com/en-us/HT201679

For scam related information from Apple including reporting scams to Apple see Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams https://support.apple.com/en-us/HT204759

I recvd an email today saying my AppleId had been used to purchase an APP that I did not purchase. Attached was a receipt that looked real. How can I find out what purchases have been made on my account? Thanks!

I mentioned above: "Did you provide any potentially damaging information to anyone? If yes, you'll need to follow up, for example, with a credit card company, Apple, your bank, etc." But, if you did not provide any potentially damaging information to anyone, then I don't think you have a problem.

Got it. I think it was an attempted scam.