What is perception and Why do we see things the way we see them?

First of all Perception is the way we choose how and what to see even if it isn't reality.

Example from the DST: first picture was talking about a cat that sees itself a lion, maybe the cat wants to see itself strong like a lion just by imagining it.

Another example from the DST: second picture was divided in two other pictures. The part in white seemed as a cup or a mug and the part in black seemed like two face of two people. That's of course my perception but other people may have seen another things because in the end, everyone has their own imagination and people don't always see things in the same way.