The first kind is "Activation Costs". These are paid when you activate ("play") a card. Activation costs cannot be negated by cards that negate the effect of a card. The second kind is "Maintenance Costs". "Maintenance Costs" are costs that are paid in order to keep a card on the field. Examples of cards with "Maintenance Costs" costs include most of the Archfiend monsters from the Dark Crisis expansion, "Imperial Order", "Messenger of Peace", "Mirror Wall", "The Regulation of Tribe", "Armor Exe", and more.