'Subject' and 'Object'

A lot of the explanations in English grammar start with the terms 'subject' and 'object' of a sentence, so it's very important that you be very clear as to what these two terms refer to.

The Subject is the noun to which the sentence's verb refers to whereas the Object is someone or something that is involved in the subjects' performance of the verb/action.

For example:

Jacob is reading a book.

In this sentence the verb is 'reading'. Now who is reading? Jacob. So the verb 'reading' is referring to the noun 'Jacob' who, therefore, is the subject of the sentence. Now what is being read? A book. So the book is involved in the subjects' (Jacob's) performance of the verb (reading) and hence is the Object.

While there are several different types of subjects and objects, you don't need to go into such depth to answer questions on the GMAT.

To Sum it Up:

1. The Subject is who/what does the action.
   
   
2. The Object has the action done upon it.