A money market account is a worthwhile investment if you value, generally, quick access to your account, a predictable APY and a federally insured account. There are other investments that may have higher rates of return, but they may also have potential risk of principal. So, a money market account may be a worthwhile investment for funds you can’t afford to risk. A high-rate money market account may be the perfect place for money that you intend to grow but may be needed in the near future.
Take the money on your bank account: What is it more than entries in a database that can only be changed under specific conditions? You can even take physical coins and notes: What are they else than limited entries in a public physical database that can only be changed if you match the condition than you physically own the coins and notes? Money is all about a verified entry in some kind of database of accounts, balances, and transactions.
The money market consists of financial institutions and dealers in money or credit who wish to either borrow or lend. Participants borrow and lend for short periods, typically up to twelve months. Money market trades in short-term financial instruments commonly called "paper". This contrasts with the capital market for longer-term funding, which is supplied by bonds and equity.