Vedana is the bare affective tone of experience, whether pleasant, painful, or neutral. Another word for this if you are familiar with qualia/phenomology science is valence.
Sitting in meditation can sometimes feel nice and pleasurable when we’re in a deep state of relaxation or absorption. This a pleasant or positive vedana.
Sitting can sometimes feel terrible if we are uncomfortable, in pain, bored or irritated by some thoughts. This is a painful or negative vedana.
Sitting can also sometimes feel neither good nor bad; we don’t mind it all that much. This is a neutral vedana. Many experiences have a neutral tone if you attend to your moment to moment experience.