A maintenance cost is a condition you must follow in order to keep a certain card on the field.
It is like a regular cost, however you are given an option to pay it or not. Some would not give you the option and you will have to pay when designated. Most maintenance cost will not destroy themselves if you do not have the sufficient cost, and will force you to pay; this can result in a game loss if you are careless.
Player A has Degenerate Circuit and Terrorking Archfiend on the Field
Player A has 1000 LP and it's the Standby Phase
Terrorking Archfiend cost is 800 LP (200 LP)
Degenerate Circuit cost s 500 LP (0 LP)
You CAN avoid paying the Maintenance Cost, but you'll will need to be crafty and use some cards outside of your knowledge.
Maintenance Costs do not start a chain.
Neither you nor your opponent cannot negate a Maintenance Cost with Skill Drain, Divine Wrath, etc.
When card destroyed by a maintenance card is not considered "destroyed by an effect". This means Continuous Trap Cards destroyed by they're maintenance costs WILL be destroyed even if Imperial Custom is face-up
The text associated with Maintanence costs are commonly
"The controller of this card pay ___ Life Points during each of his/her Standby Phases (this is not optional)
The second doesn't have a set text but, it is phrased "you must do this action or destroy this card."
Ex. Koa'ki Mieru Valafar
Text: During each of your End Phases, destroy this card unless you send 1 "Iron Core of Koa'ki Meiru" from your hand to the Graveyard.
You can Tribute Summon this monster by Tributing 1 "Koa'ki Meiru" monster. This card cannot be destroyed by the effects of Trap Cards. During battle between this attacking card and a Defense Position monster whose DEF is lower than the ATK of this card, inflict the difference as Battle Damage to your opponent.
Ex. Mirror Wall
Type: Trap (Continuous)
Text: Halve the ATK of all your opponent's attacking monsters. Pay 2000 Life Points during each of your Standby Phases. If you do not, destroy this card.
If I missed anything or if you have any questions or concerns, please reply to this topic.