The core experience is like a North Star defining the main purpose of your game. It's a mantra that should always be used in your development process. Use a defined core experience to help you make other decisions as you get deeper and deeper into your game mechanics.
Too often game companies use fast-follow techniques and simply try to copy what other games are doing. They often do not truly understand what the core experience should be. When this occurs they have difficulties replicating long term success that other games have seen (despite short term pops).
The core experience also needs to be the right size / scope. If you define a core experience that is too broad, your game will lack focus and won't find a successful demographic of players. Likewise if you go too specific or rigid, you may limit your audience so much that you can't find enough players.
Let's look at an example. If you were building a car company, the core experience you are providing is transportation. Simply saying that you are building a car to provide transportation is too broad however. You have to refine it's scope so that you can make meaningful decisions.
A car that focuses on transportation for large families will have very different goals than a car that focuses on transporting heavy equipment or a car that focuses on transporting people in the speediest fashion possible.
In this example above, we have three very different core experience definitions. They can be summarized as a car designed for economics, a car designed for power and a car designed for speed. As the designers evaluate materials, engine capabilities and so forth, they will make different decisions for each of these 3 different car designs.
Likewise in our game design journey. Start by defining what you want your core experience to be. Your first statement might be:
Great! However, this doesn't give us much direction, in fact it gives us no direction. Let's try something with some more specifics in it:
Much better! However, we still need to refine it a lot. Which this statement is a good starting point - there isn't a lot here to help us with the designs, the engine, the art style, etc. Here are some areas of the game play that you should ask yourself about to help you decide what type of game experience you want to create:
These are just a sampling of questions to help you think about the core experience for the game. They are not requirements. However using this list, we can easily refine our game idea into the following:
This is a good statement about our core game experience - it can help us make a lot of decisions. In this game we know that we will support player progression, character development, social gameplay mechanics and so forth.
We can still take it further though and provide more definition without hamstringing our designs. For example: "battle against each other". Are we referencing the dragons battling against each other or the player battling their dragon armies against each other, etc. When revising, remove fluff / filler words and try to get straight to the core of your desired design.
This statement is a great example of a core game experience that will help you make a lot of decisions down the road. It can of course continue to be revised and improved - but this starting point is a much stronger starting point than wanting to create a popular dragon fighting game. This will help your engineering team pick the right engine, your art team pick the right art style and so forth.