Discursive writing presents an argument related to a given topic. It can either examine both sides of the issue in a balanced way or argue persuasively on one side only.
It is important to write formally in a discursive essay. This means you should write in complete sentences, using full words and expressions and standard English. Contractions should be avoided. For example, 'is not' should be used instead of 'isn't'.
It is advisable to try and avoid expressions like 'a lot' or 'lots of'. More formal expressions such as 'many', 'much', 'a number of', or 'numerous' are more suitable for discursive writing.