Ontology is the craft (some call it study) of posing things to be the case (true). Posing, like artists with their sketch doll, but we do it in thought. In doing that, we use the verb "to be" and its derivatives. We do it in speaking, but we also do it in thought, and without thought. We pose the world "to be."
Imagine yourself invested with, for instance, a fear of something, it doesn't matter what. All the things that can be proposed about that situation in words are things that can be believed. Of those things that can be proposed, some will be true and some will not. That you know which are true are not doesn't matter [and can even be a contradiction]. If they appear to be the case, you'll believe them. But of all the things you believe, the ones that are true are knowledge*. You don't have to know which are knowledge--to you, knowledge and belief may appear identical. Knowledge will be the belief that is posed "to be," in thought, and without thought. Propositions: You are afraid. Fear has gripped you. You are going to run. The monster is chasing you. These propositions, as they represent the world (in thought), are worded objectively to be the case, that are the case, and so we house them in the verb "to be."
You see, it's not really about you, or me, or any of us. We house them in the verb "to be" because we cannot but have identified truth about them that is beyond us. They are the world to us.
*The case of "fiction" was devised just for the ability to pose things as if true. But the case of "real" is the case where the truth of a thing is beyond us.