Jesus was at the temple with the disciples. Here he witnessed something which he used to teach the disciples about giving.
He sat across from the treasury of the temple and watched many rich people put in large sums of money.
Then a poor widow came along and put in two small copper coins.
Jesus teaches the disciples that the woman gave more than the rich.
The poor woman, as a widow, would have had no source of income after her husband’s death. Therefore the two small copper coins were all she had - and yet she offered them to God.
The rich, on the other hand, had a lot of money to spare. So what they offered to God was just loose change, money they did not depend on.