What info can someone get if I give them my apple id?

If you’ve given them the email and the password, and don’t use AppleID 2 factor authentication, they can simply use your AppleID exactly as you do. Any service requiring an AppleID login only knows the AppleID, not who is using it. Someone with your AppleID can restore your iCloud backup to their device, access your iCloud email, contacts, notes. They can login to any Apple online store and buy things with your AppleID and payment method.

Never share an AppleID with anyone, for any reason. And enable 2FA as well so that just your password is insufficient to login.

Do they just know the email associated with your Apple ID, or did you give them the password as well? If just the email, you don't have much to worry about, but if they know the password, change it immediately at https://appleid.apple.com.

I'd also recommend setting up 2FA (two-factor authentication) for your Apple ID if you have not already: https://support.apple.com/en-us/HT204915.