What's the difference?
This is used in the meaning ‘the result that you intend to get when doing or planning something’.
Now, all these words mean this and so are useful synonyms, but of course, they have subtle differences.
If you say that you have a target, for example: Our target today is to shift 30,000 items of warehouse stock ready for distribution, you mean that this is the exact result you want to get by doing something. It is also often used when talking about trying to get a certain amount of money, usually by doing something by other things that will help get this money: The target for the appeal is £20,000. (Perhaps through the public giving money to this charity.) The government’s target of $23 million is an overestimate. (An amount of money the government are, perhaps, trying to save, usually by some kind of restructuring.)
Now if you have an aim, then this is what you are hoping to get by a plan, action, or activity, and you want to do this. It may or may not succeed: Our aim is to increase spending by 30%. The aim of the course is to improve your conversational skills.
But if you have a goal, then this is what you hope to achieve in the future, and this may take a lot of time: Our goal is to become the number one organisation in this field of industry. The goal of this government is to make poverty a thing of the past. Some directors have unrealistic goals in what they hope to achieve when it comes to telephone selling.
So in summary:
Target: the exact result of what you want to get.
Aim: what you hope to get and you want to do this.
Goal: what you hope to get, but may take a long period of time.