When talking about the world, there are a collection of terms used, such as truth, fact, assumption, assertion, theory, scientific theory, scientific law, hypothesis, premise, inference, conclusion, etc.. While we have many words, it breaks down into two concepts: observations & inferences.
Observations are direct experiences that are not derived from other experiences. That's what it means in this context. It's the initial material for what you infer things from. As an observer, all we can do is make observations (personal experiences) and make inferences about them. We collect observations over our lives, and continuously infer conclusions based off of them. This is true for religion, philosophy, and science.
Religion, Philosophy, And Science
If someone has a spiritual experience that causes them to believe in (x) religion, then they have inferred that (x) religion is true from that personal spiritual experience. They may also personally observe other people coming to the same conclusion who have had a similar experience, which may also be used to strengthen their own inference. These are observations (personal experiences) as well. When you personally see and hear someone, or see and read an article, these are personal experiences you have. You collect these experiences, these observations, and construct your own model of how the world works.
In philosophy a lot of logic is used. You may come up with your own logical progression or come across a logical progression that makes specific conclusions. What is happening, is that you're observing yourself or someone else making these arguments. These experiences become a part of how you model the world.
In science, there is an extra focus on observation. Scientists create special tools, like telescopes, to make more observations. They create experiments and measure things to make more specific observations. And then they use these observations to make better inferences about the world.
As observers, we create models of the world, based on a set of observations and inferences. Even at a subconscious level, we build models. Your visual field is a 3D model of the external world. You don't consciously control your visual field. You don't consciously observe the electric signals coming from your eyes and infer a 3D model. It all happens without you having to think about it.
When you consciously think about your observations, you can make more inferences. Such as inferring that since those electrical signals could possibly come from a program, that you cannot be certain that those initial electric signals came from the world as you know it.
Logic is the study of arguments. An argument is composed of two things: propositions and an inference. A proposition is a statement that can be true or false. Propositions accepted as true in the beginning of an argument are known as premises (input), and the proposition inferred (relation) from those premises is called the conclusion (output).
As an observer, you often use your observations as input (premises) and relate (infer) it to a output (conclusion). However, in logic, a premise does not have to be an observation. It can be the conclusion in a different argument. A premise is an input, be it an observation or an inference from another observation.
A scientific theory is a model. It's a set of observations and inferences. That is to say, when you take it upon yourself to learn a scientific theory, you will be learning about observations called facts, and will also learn about the inferences from those facts.
A good example of this is the fossil record. The fossil record is a huge collaboration of observations that have been made by paleontologists. There are hundreds of thousands of observations that have been made. They use these observations to infer the existence of species that no longer exist. And from that inference, amongst other observations, they infer a timeline of when they did and did not exist. They keep collecting observations and create a model called the theory of evolution.
In the end, when we communicate, all of it is through language when it comes to describing the world. We may use pictures, such as graphs, but they are all explained using language. So a scientific model, while it may be derived through the personal experiences of thousands or millions of people, it consists of strings of symbols written across your computer screen or paper.
While your brain may create models, such as your visual field, with trillions of neural connections, we consciously create models with arguments. We write propositions and conclusions. We, as observers, use language to communicate how the world works. And just as an observer has limitations, such as not being able to bridge that gap between the innerworld and outerworld, language may have its own limitations that you are not aware of.