There are four types of graphs in IELTS Writing Task 1: line graphs, bar charts, pie charts and tables. 

Each type of graph has its own set of rules and conventions that you need to follow in order to score well.

Line graphs are the most common type of graph that you will encounter in Task 1. They show how something has changed over time, usually in relation to another variable. For example, you might be asked to show how the number of hours of sunlight has changed over the course of a year, or how GDP has changed over the past decade.

Bar charts are another common type of graph in IELTS Writing Task 1. They are used to show how something is divided into different parts or categories. For example, you might be asked to show the market share of different mobile phone brands, or the percentage of people who prefer different types of food.

Pie charts are used to show how something is divided into different parts or categories, but they are only used when there are a small number of items being compared. For example, you might be asked to show the percentage of people who prefer different types of food, but a pie chart would not be used if there were 20 different types of food being compared.

Tables are a less common type of graph in IELTS Writing Task 1, but you may still be asked to describe one in your test. Tables are used to show numerical data in a tabular format. For example, you might be asked to show the population of different countries, or the average monthly expenditure of a family.