Occasionally, there are issues within your various Credit Reports. This could be any of the following:
There's an address you're no longer associated with (or never were)
That address could simply have a typo, and needs correction
There's an Employer you're no longer associated with (or never were)
Maybe there are incorrect dates for your time there
There are credit, bank, or loan accounts that you don't recognize
If any of these are very recent, that could be a major red flag that your Identity has been compromised.
Also note, sometimes the main bank/brand name you know might show up as a different name on your credit report. Always double-check to make sure!
The reasons for a dispute are not limited to the above reasons, but these are the most common. The best way to solve this is to file a dispute directly with each of the credit bureaus. (If the issue does not exist with all 3 credit bureaus, then you would only need to file the dispute with the ones which show the discrepancy.)
Here's how to do this online with each of the major credit bureaus: