Some spells and abilities that give you {E} may require targets. If each target chosen is an illegal target as that spell or ability tries to resolve, it won't resolve. You won't get any {E}.

{E} is the energy symbol. It represents one energy counter.

Energy counters are a kind of counter that a player may have. They're not associated with any specific permanents.

Keep track of how many energy counters each player has. Potential ways to track this include writing theme down on paper or using dice, but any method that is clear and mutually agreeable is fine. (At higher levels of tournament play, dice may not be allowed for tracking counters that players have.)

If an effect says you get one or more {E}, you get that many energy counters. To pay one or more {E}, you lose that many energy counters. You can't pay more energy counters than you have. Any effects that interact with counters a player gets, has, or loses can interact with energy counters.

Energy counters aren't mana. They don't go away as steps, phases, and turns end, and effects that add mana "of any type" can't give you energy counters.

Some triggered abilities state that you "may pay" a certain amount of {E}. You can't pay that amount multiple times to multiply the effect. You simply choose whether or not to pay that amount of {E} as the ability resolves.

Some triggered abilities that state that you "may pay" a certain amount of {E} describe an effect that happens "If you do." In that case, no player may take actions to try to stop the ability's effect after you make your choice. If the payment is followed by the phrase "When you do," then you'll choose any targets for that reflexive triggered ability and put it on the stack before players can take actions.

If a spell or ability with one or more targets states that you "may pay" some amount of {E}, and each permanent that it targets has become an illegal target, the spell or ability won't resolve. You can't pay any {E} even if you want to.

You may activate a crew ability of a Vehicle even if it's already an artifact creature. Doing so has no effect on the Vehicle. It doesn't change its power and toughness.

For a Vehicle to be able to attack, it must be a creature as the declare attackers step begins, so the latest you can activate its crew ability to attack with it is during the beginning of combat step. For a Vehicle to be able to block, it must be a creature as the declare blockers step begins, so the latest you can activate its crew ability to block with it is during the declare attackers step. In either case, players may take actions after the crew ability resolves but before the Vehicle has been declared as an attacking or blocking creature.

If a permanent becomes a copy of a Vehicle, the copy won't be a creature, even if the Vehicle it's copying has become an artifact creature.

When a Vehicle becomes a creature, that doesn't count as having a creature enter the battlefield. The permanent was already on the battlefield; it only changed its types. Abilities that trigger whenever a creature enters the battlefield won't trigger.

Each Vehicle is printed with a power and toughness, but it's not a creature. If it becomes a creature (most likely through its crew ability), it will have that power and toughness.

If an effect causes a Vehicle to become an artifact creature with a specified power and toughness, that effect overwrites the Vehicle's printed power and toughness.

Vehicle is an artifact type, not a creature type. A Vehicle that's crewed won't normally have any creature type.

Once a player announces that they are activating a crew ability, no player may take other actions until the ability has been paid for. Notably, players can't try to stop the ability by changing a creature's power or by removing or tapping a creature.

Any untapped creature you control can be tapped to pay a crew cost, even one that just came under your control.

You may tap more creatures than necessary to activate a crew ability.

Creatures that crew a Vehicle aren't attached to it or related in any other way. Effects that affect the Vehicle, such as by destroying it or giving it a +1/+1 counter, don't affect the creatures that crewed it.

Once a Vehicle becomes a creature, it behaves exactly like any other artifact creature. It can't attack unless you've controlled it continuously since your turn began, it can block if it's untapped, it can be tapped to pay a Vehicle's crew cost, and so on.

Multiple instances of lifelink on the same creature are redundant.