This is from my note,which I collected from diff forums. Hope it will be useful
An appositive is a re-naming or amplification of a word that immediately precedes it.Absolute phrases on other hand do not directly connect to or modify any specific word in the rest of the sentence; instead, they modify the entire sentence, adding information. Usually (but not always, as we shall see), an absolute phrase is a group of words consisting of a noun or pronoun and a participle as well as any related modifiers.Absolute phrases contain a subject (which is often modified by a participle), but not a true finite verb.(GARDEN OF PHRASES)
1. Guillermo, his arm in pain, Guillermo strode out of the building. (Little modified exp of absolute phrase of MGMAT SC
4th edition, pg number. 291 )
2. The coach, an old classmate of mine, was not pleased. (exp of appositive of MGMAT SC
4th edition, pg number 292)MGMT STAFFYou need to use meaning to distinguish between appositives and absolute phrases. Since absolute phrases are modifiers, they will usually contain a different kind of information than an appositive. In sentence 1, "his arm in pain" modifies Guillermo. It wouldn't make sense to say that Guillermo and "his arm in pain" are the same thing. (Note also that the sentence begins with "His arm." It would not be correct to place the name Guillermo both before and after the phrase.)
In the appositive example, the coach is also an old classmate. Since it makes sense for a coach to be the same as an old classmate, we can see that this is an appositive.
The second example of an absolute phrase ("The car fell into the lake, the cold water filling the compartment.") is a bit more tricky. It is possible for "the lake" and "the cold water filling the compartment" to be the same thing, so we could interpret this as an appositive. However, since a lake is something everyone should be familiar with, it makes more sense to read this as an absolute phrase. The second portion of the sentence does not modify the word "lake," but rather describes the result of the event mentioned in the first half of the sentence.
To sum up, you know you are dealing with an appositive when it seems logical to think of the two adjacent nouns as identical. If the noun in the modifying phrase is *doing* something ("He stepped out of the car, his leg bleeding badly."), you are probably dealing with an absolute phrase.