Painting is a way to express how we feel about things which we see in our everyday world.. This expression may be fairly literal (representational) or it may be an interpretation of a feeling or idea (abstract) depending on the artist's mode of expression or their intention. Or even their own personality which inevitably comes through in their work, much like a person's individual handwriting.
"... the artist can never be greater than the thing before him - which is nature, whatever else it is, and nature contains all mysteries." - Robert Henri