We need to start by having a look at a typical exam question:
First some context is given:
'... you have been part of a discussion ...'
Then you are given a question:
Do you think it's better to stay in your own country for your holidays, or to visit another country?
Then you are given 2 ideas to discuss, and you are required to create your own idea, which will be the third one.
It is made clear just above the question that you are expected to cover all the points:
'Write an essay using all the notes, and give reasons for your point of view.'
Then you are told the document needs to have between 140 and 190 words. This means less than 130 words and more than 200 words will lose you marks.
And finally, you are told you MUST use correct grammar, accurate spelling and punctuation, and the style of your document must be appropriate.
Using these ideas let's create a basic essay which tries to satisfy these requirements.