The writing task 1 of the general module is a letter that test takers have to write in a minimum of 150 words and in 20 minutes. Test takers are penalized if they write less than 150 words. Candidates do not require to write any address in the letter. You should not spend more than 20 minutes on task 1 as it will leave you with less time for task 2 (essay), which is lengthy and hold more band scores than task 1. For practising IELTS letter question, click here. The below-given diagram describes to you about the different types of letters and how to recognise them.