Magic: The Gathering concept. If you have any mana on your mana pool at the end of a phase, then you lose 1 life for each mana point in your mana pool and that mana is lost.
Some of the cards which most frequently produce mana burn are colorless mana producers such as Sol Ring or Mana Vault (you may need just some of the mana, and generally it's worth losing a couple of life points), land enhancers such as Mana Flare or Gauntlet of Might (the same), strange creatures such as Su-Chi or Cathodion (which are a kind of unstable "mana bombs"), and other triggered mana generators.
It's not a common situation, but mana burn can even be useful in some cases, the most obvious one being in combination with Mirror Universe.