The CP2000 notice means that the income and/or payment information the IRS has on file for you doesn’t match the information you reported in your return. Per the IRS, the CP2000 indicates:
The income or payment information we have on file doesn't match the information you reported on your tax return. This discrepancy may cause an increase or decrease in your tax, or may not change it at all.This could mean the IRS has received forms that weren't included on your tax return. Or, you included information on your tax return that the IRS did not receive.
Here is a TurboTax FAQ about CP2000:
https://ttlc.intuit.com/replies/5689447
You can also read more at this IRS link: https://www.irs.gov/individuals/understanding-your-cp2000-notice