It should be no surprise that Teilequin is not the only world in the great, expansive cosmos, nor is the plane in which it resides the only plane of existence. While this story has little reason to go into the complexities of everything in the great beyond, there are some aspects of the way the universe is set up that might be useful to know. What follows is a brief primer detailing the things that are most likely to be relevant to you during the course of this roleplay.
Planes: The world of Teilequin is situated on the Material Plane. Simply put, the Material Plane is the natural world that we all live in, dealing with things such as matter and physics and so forth. It is tangible, physical, readily perceptible with your five(?) senses. But it is not the only plane of existence. Providing a full list of every possible plane that actually and/or theoretically exists would be a bit much, but it is worth covering at least one other plane: the Ethereal Plane.
Imagine that the Ethereal Plane exists in the exact same space and time as the Material Plane, but possesses and embodies all the properties that are absent in material, physical things. In essence, this would be the intangible concept like "spirit", "faith", or "belief", or whatever similar terms you might use. The Ethereal Plane extends across any and all worlds in the Material Plane, but the form it takes and the function it serves will depend on which world you're looking at. In a sense, it is a reflection of what lies in the Material Plane, and each world will cast its own unique reflection.
Suffice it to say, the Ethereal Plane around Teilequin is a composite reflection of the people that live on that planet. So basically, it takes shape based on the beliefs and ideas of the people living on Teilequin. And because of that connection, it is possible to reach across the planar boundaries and tap into the Ethereal Plane from the Material Plane, if you know the proper methods.
Demesnes: Entities that reside in the Ethereal Plane are often much more attuned to magic and the power it provides. Those entities with a lot of power are able to sculpt their own personal territories, or sometimes even their own worlds. Such places of power are beholden entirely to their creators, and provide these entities with a domain of safety and strength in times of need. These places of power are called demesnes.
A demesne is home to not only the thing that created it, but also any entities that pledge themselves in service to the creator. The number of entities living in a demesne, along with the reach of its territory, is a good measure of how powerful the presiding entity will be. This is often the barometer used by Conjurers attempting to call forth spirits to fight for them. But it's always a risk when interacting with a demesne - it might pull you in. And the rules of a demesne aren't necessarily those you're familiar with.
Destination: Everyone wonders at some point or another: where do I go when I die? In Teilequin, the answer is something that can actually be explained, although scant few people on the planet actually know this truth. When you die, your soul will pass from the Material Plane to the Ethereal Plane. But where exactly it goes will depend on belief. In a way, your destination in the afterlife is determined by what amounts to a popularity contest.
To elaborate, you will go where your fellow people think you should go. Depending on how you choose to live your life, you will make various impressions on various people. Each of the people you impact will probably have their own beliefs about what will happen to you when you die. Every time you impact a person, an eternal connection is formed, and that person's opinion about you will affect the fate of your disembodied soul. If most people that know you think you ought to go to hell because you're a right bastard, then you will.
Naturally, this can lead to some interesting results. For instance, it's entirely possible that a complete monster could make it into an eternal paradise just by effectively deceiving the people that know him. Likewise, genuinely good people who are thought to be wicked and villainous could wind up condemned to a cruel hell. Again, it all depends on the cumulative beliefs of the people you know.
But what if you're a loner? What if you go through life painstakingly avoiding anyone and everyone, never saying so much as a word to another person, or even drawing their attention? What if you are so invisible that at the end of your days, the cumulative number of people who have an impression of you is zero? Well, in that case... your soul would cease to exist. so hopefully you get out there and talk to some folks.