There are 4 primary danger levels to an entity
The first, being harmless, the second being mildly hostile, the third being dangerous, and the forth extremely deadly. They are usually split up into classes (class 1, 2, 3, 4). A class 1 entity cannot or will not hurt you. There are not many class 1 entities, so if you find one, take advantage of it. A class 2 entity most likely wont hurt you unless you harm it, or do something to annoy it or bother it. A class 3 entity will harm you if it sees you, you may be able to get away from it, hide from it or distract it, given the supplies that you have. Class 3 entities are the most common in the Backrooms, so always be aware of your surroundings. The final class of an entity (class 4) is the most dangerous of all. Most class 4 entities will kill on sight, or chase you down until finally, you get caught. Class 4's are often smarter than other entities, and usually there is no way to hide from them, so if you see one, it most likely has seen you.