Can any one please explain the usage and meaning of "He is polite" and "He is being polite".
He is polite.
This is a simple statement describing a property of this person. You could also say:
He is tall.
He is Chinese.
These are things that are generally true about this person at any given moment.
He is being polite.
This describes an attribute of what this person is currently doing. "He" may generally be a very impolite person or not, but at this specific moment, he is being polite.
Actually, the sentence has also an implied meaning: he's being polite implies that he is saying something, or reacting to a situation, in a way that does not reflect his real intentions, but he is, for the sake of politeness, saying or doing something he doesn't fully agree with:
He agreed that John's idea was a good one, but he proposed a completely different approach yesterday. I guess he's just being polite.
In this case, he probably disagrees with John's idea, but for the sake of politeness he tells John the idea has merit.
"He is polite"
means what it appears to mean, i.e. it is in his nature to be polite.
"He is being polite"
means that he is making a particular effort to appear polite right now, despite the fact that the situation is one in which a lack of politeness would be understandable — for instance, because somebody has just insulted him, or has said something totally stupid, or is behaving badly in some other way.
“He is polite” means the person always, or at least generally, applies good manners, etiquette, and other informal social rules.
“He is being polite” means the person is applying good manners or etiquette on this specific occasion.
The latter sentence may also imply that he has expressed an falsehood as some kind of white lie. Example: “When he told you that you are an excellent singer, he was merely being polite.”