In English, sentences often have a subject and an object. 

The subject is the person or thing that is doing the action. 

The object is the person or thing that is receiving the action.

Lets look at two examples:

➜ E.g. The cow eats grass.

In this example, the subject is the cow because it does the action of eating the grass.

The grass is the object because it was acted upon.

An easy way to find the subject and the object is to first find the verb in the sentence, then we can ask “who?” and “what?”.

So in the example above, the verb is eats. After this, we can find out who carried out this action by asking “who eats?”. The answer is the cow. Lastly, we can find the object by asking “what does the cow eat?” the answer is the grass. 

➜ E.g. James drove the car. 

In this example, the subject is James because he did the action of driving. The object is the car because it was acted upon.