Motivation as a topic is quite vast and is used in different context. Human motivation is simplistically defined as a set of reasons that determines a person to act or engage in a particular action or behavior. There are many proposed theories of motivation that define and explain different attributes of motivation and different styles used to motivate people.
Motivation plays a very important role in public speaking. Here, motivation is defined as a communication that leads a person to a particular thought process, an action or a reaction.
From the theories of motivation, it is clear that motivation is rooted in all basic needs of human kinds and other intangible needs such as greed or altruism, morality etc.
Intrinsic motivation is defined as motivation that includes involvement in thought process, behavioral pattern action, or reaction. Here, there is no external incentive for the actions you do. For example, a person may be intrinsically motivated to donate to an NGO because he feels happy about it internally. He did not donate the money because he attended a motivational talk or a lecture by that NGO. Similarly, a person paints because he is internally motivated to do so.
Extrinsic or external motivation is the very opposite of intrinsic motivations.
Here, it is circumstances, environment and situations that push you to a certain action. Intangible or tangible rewards and punishments also lead you to a behavior which results in external benefits.
For example, a student may be motivated to study because he is promised a watch on scoring X percentage. Similarly, an employee is motivated to work more because every time he performs well, he is praised by his boss.
In this way, tangible attractions like rewards, prizes, money etc become a great source of motivation whereas intangible benefits like adulation, respect, recognition and praise are also an important source of motivation.