A dematerialised (Demat) account is an account that allows you to hold your financial instruments electronically. If a savings account is used to hold your money, a demat account is used to hold your shares.
It is important to note that as an investor, you cannot trade in the stock market without a demat account. With a demat account, you can hold the certificates of all your financial instruments such as Mutual Funds, Exchange Traded Funds (ETFs), Shares and Bonds online.