Contractions are short words that are made by combining two words. This is often done by deleting certain letters and replacing them with an apostrophe (e.g., “do not” becomes “don’t”).
Although contractions are common in everyday speech, they should generally be avoided in formal or academic writing. However, there are exceptions (e.g., when writing dialogue in a story or directly quoting an author who uses contractions in your paper).
A good rule of thumb is to consider your audience and the intended effect of your writing when deciding whether to use contractions.