There are 6 types of essays in IELTS Academic or General Writing Test (Task 2):

Agree or Disagree Essay: In this type of essay, you will be given a statement and asked to agree or disagree with it. You will need to present your arguments and support them with examples.
Discussion Essay: This type of essay requires you to discuss both sides of an issue and present your opinion. You will need to present the pros and cons of the topic and give your opinion with supporting evidence.
Advantage and Disadvantage Essay: This type of essay requires you to discuss the advantages and disadvantages of a particular issue or topic. You will need to present your arguments for each side and support them with examples.
Problem and Solution Essay: In this type of essay, you will be given a problem and asked to suggest solutions. You will need to present the problem, explain why it is a problem, and provide solutions to solve the problem.
Two-Part Question Essay: This type of essay requires you to answer two questions in one essay. You will need to answer each question separately and provide supporting evidence for each answer.
Opinion Essay: In this type of essay, you will be asked to give your opinion on a particular topic. You will need to provide supporting evidence for your opinion and explain why you hold that opinion.