Typically, 1099-G is used to report compensation from unemployment benefits, along with tax refunds issued by the state or local government.
If you receive compensation from unemployment, you are required to pay taxes on the income. You can find the total amount of money paid to you throughout the year in box 1 of the 1099-G.
If you received state or local tax refund, box 2 of the 1099-G will show any money paid to you. Just because it's listed on the 1099-G doesn't mean you will be required to report the amount on your federal tax return. If you took the standard deduction previously, you can ignore box 2. However, if you opted to take an itemized deduction in relation to payment of state or local taxes in prior years, you will need to report the amount.