These are the three modes (gunas) of material nature. People are influenced by these modes and certain modes influence people in certain ways.
The person under the influence of the sato gun is likely to be peaceful, inclined toward living according to dharma. Sato gun gives one clarity, peacefulness, calmness and purity. Saatvic gun persons avoid eating meat or intoxication (drugs, alcohol, illicit relations forbidden in dharma), their diet is likely to be grains, fruits, vegetables, water etc. They may be less materialistic when compared to the other persons under the influence of the tamo and rajo gunas. The sato gun brings goodness and peace in a person, purity of thought, action and heart are due to the saatvic gun.
Rajo gun is related to the quality of passion. It's the middle ground between sato gun and tamo gun. It brings about anger in mind and drags a person down making them restless. It is also responsible for making a person work and not just sit idle.The tendency to look into the faults of others arises from this gun.
Tamo gun brings about darkness and ignorance. Tamo gun persons are likely to be meat eaters, I think. Quick to anger maybe but deffinitely less peaceful/calm than the sato guni persons.
It is possible to progress to one gun to the other and also fall from the satvic gun to the rajo and tamo. Sato gun is the purest of the three gunas and more desirable than the other twon.