What is the difference?

What is the difference among between these three words? I think these are quite similiar. 
1) purpose
2) object
3) objective

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You are correct, they are very similar.  The "purpose" is why you are doing something.  The "objective" is what you are trying to do.  Here are some examples:

"The purpose of soccer is to have fun.  The objective in soccer is to kick the ball into the net."

"The purpose of my study is to learn English.  My objective is to pass the IELTS examinations."

The word "object" can <em>sometimes</em> be used in place of the word "objective".  However, the word "object" has many meanings, whereas "objective" has fewer meanings.  Therefore, your sentence will be clearer if you use the word "objective".

What is the difference?

What is the difference among these three words? I think these are quite similiar

purpose - The purpose is the reason that you are doing something.

object - The goal of what you are you doing.

objective - The thing thrying to be obtained.

I would almost always use objective. 

Here is an example: 

The object of basketball is to get the ball through the hoop.

or

The objective of basketball is to get the ball through the hoop.

Objective sounds nicer and cleaner. Really Object and objective mean the same thing but objective is just a better word for it. Hope this helped!