The money you invest on certificates of deposit is protected by the FDIC (Federal Deposit Insurance Corporation). There’s an insurance of up to $250,000 for your CDs.
The standard deposit insurance coverage limit is $250,000 per depositor, per FDIC-insured bank, per ownership category.
The FDIC insurance covers not only CDs, but checking accounts, savings account and money market deposit accounts.
The purpose of this FDIC insurance, is to protect your money (capital and interest) in the event that a bank fails.
More information can be found here: https://www.fdic.gov/deposit/deposits/faq.html