What is behavior?
Behaviour is how an organism changes and responds to its environment within the lifetime of an individual organism.
Plant behaviour tends to be more limited compared to animal behaviour because plants are mostly sessile (don't move around much). Because of this, plants never evolved a nervous system or a brain. A main behaviour of plants is to grow towards sunlight so that leaves can photosynthesize and make nutrients for plants. Likewise, they grow roots downward that try to find water and nutrients. Some flowers are phototrophic and track the movement of the sun during the day.
Animal behaviour is called "ethology" and is more complex, Animals move around in their changing environment and must react quickly to eat or be eaten, find food/water or a mate! Consequently, they have evolved brains to help make these quick behavioural decisions that try to keep them alive and able to reproduce.