Stimuli refer to the response to the environmental signal by an organism. The stimuli are of two types, external stimuli and internal stimuli.
When we wish to reach for the Peach in the bowl, both external and internal stimuli will play a very important role. If our body sugar level goes low, we feel hungry. This will result in the natural temptation for the fruit. Such temptation is called internal stimuli. However, if we see a fresh Peach in the basket of fruits, our external stimuli will make us tempt for the fruit. But if the Peach is spoiled at places then our external stimuli will make us reject the fruit, in spite of of our hunger. Hence, both the stimuli play vital role in deciding our actions.