what is FDIC-insured IRAs?

an IRA is an Individual Retirement Account. IRA's are tax shielded type of accounts. In other words, when you gain money in that account, you won't have to pay taxes on it when you withdraw money (for an Roth IRA) or will grow tax free (for a Traditional IRA).

FDIC is the government control, you usually see them at major banks. They state that you cannot lose your money (up to 250,000 per account) if the company (such as the bank) were to go bankrupt. This does not include losses from trading in the stock market.

So putting that together, your IRA is FDIC insured, meaning if the you have money in TDAmeritrade, and you traded stocks/funds, and lost money, that is not FDIC insured. But if TDAmeritrade company itself went bankrupt, you would not lose your money in that account.