EXP share [ee-ex-pee-shehr]
noun
1. Pokémon. a) This item, when held by a Pokémon, allows it to earn half the experience gained from defeating a Pokémon, regardless of if it was used in battle or not.
b) In Pokémon X & Y, the item is now a Key Item and can be
turned on or off. Doing so results in all Pokémon receiving the experience. They
receive 100% of the experience if in battle, and 50% of the experience if they were not in
battle.
EX. I've always been a big proponent of EXP share because it made training up lower level Pokémon much easier. As a hold item, it allowed you a small boost to training up a Pokémon without having to swap it out and, if you did throw it out first, it got even more experience. When I first heard they were changing EXP share, I must admit... I was a tad nervous.
Heck, when they change any item in Pokémon, it's a little worrying but, and I gotta hand it to them, they usually change things for the best.
In X & Y, the EXP share gives all Pokémon in your party half the experience they would've earned battling. This means all Pokémon battling get 100% experience and all not battling get 50%. This is a substantial boon to those wanting to level a team quickly and makes the game far less of a grind. In fact, with EXP share on, it won't take long for your Pokémon to be ten or more levels above everything you're fighting and, somewhat curiously, your only options to get around this issue is to either turn it off, which seems to just waste your time, and to constantly rotate your team out. The latter solution is what I went with in how to deal with the change.
And I really do have some mixed feelings about the situation: on one hand, the negatives are that you wind up having less of a strong relationship with the usually small team you would run but, on the other hand, it has made the game a lot easier and forced me to use a lot more Pokémon. The fact that I have like a dozen rotating Pokémon gives an experience much more like Ash Ketchum in the anime, except I have no staple like Pikachu. It's a mixed bag, but ultimately a good inclusion in the latest games.