Someone sentient is able to feel things, or sense them. Sentient usually occurs in phrases like "sentient beings" and "sentient creatures," making it clear that things that don’t have life don’t have feelings. Explain that to a pet rock.
Sentient comes from the Latin sentient-, "feeling," and it describes things that are alive, able to feel and perceive, and show awareness or responsiveness. Having senses makes something sentient, or able to smell, communicate, touch, see, or hear. Whether or not plants and living things other than animals and people are sentient depends on whom you ask.