Texts that deal with facts, opinions and the real world are usually described as non-fiction. Different text types, or forms of non-fiction have particular conventions. These are the typical or expected features of a form and include structure, language and tone. For example, a newspaper article usually has a headline, uses formal language and takes a serious tone. A political speech usually addresses the audience directly, includes persuasive language and often has a rousing tone.
With all writing tasks it is important to consider:
Your reader might be one particular person, as with an email or letter. Or it might be a broader group of people, as with an article or speech.
Having a clear purpose will allow you to select language best suited to your task. For example, if your purpose is to entertain, your tone might be light-hearted. If your purpose is to persuade, you might include rhetorical devices.