The CS50 credit card problem is a programming challenge that asks you to implement a program that validates a credit card number and determines its issuer. The problem requires you to write code that performs several tasks, including:

1. Prompt the user for a credit card number
2. Check if the number is valid according to Luhn's algorithm
3. Determine the issuer of the credit card (i.e. Visa, Mastercard, American Express, etc.)
4. Print the issuer of the credit card to the console.

This problem is often used as an exercise to test skills related to input/output, string manipulation, and basic programming concepts.