What are “work credits” in Social Security Disability Cases?

What are work credits in a social security disability claim and how many are needed?
https://pedlaw.com/blog/what-are-work-credits-social-security-disability-cases

What to do if your Social Security Disability Claim is denied.

Social Security Disability denied your claim. Now what?
https://pedlaw.com/blog/what-do-if-your-social-security-disability-claim-denied