Aristotle has just finished discussing the difference between a problem and a thesis. He is discussing this in order to explain how we gain the arguments we need to argue well. He does this in Topics, Book 1.
Having made these distinctions, we must distinguish how many species there are of dialectical arguments. There are induction and deduction. Now what deduction is has been said before- induction is a passage from particulars to universals, e.g. the argument that supposing the skilled pilot is the most effective, and likewise the skilled charioteer, then in general the skilled man is the best at his particular task. Induction is more convincing and clear: it is more readily learnt by the use of the senses, and is applicable generally to the mass of men- but deduction is more forcible and more effective against contradictious people.
Now that we have explained and distinguished between propositions, problems and theses we should determine how many kinds of dialectical arguments there are. There are two kinds: deduction and induction. Aristotle has already explained what deduction is. Induction, then, is the argument from individual examples and things to universal truths. For example, we might argue that In general, skilled people are better than unskilled people at a task by arguing that skilled pilots are better than unskilled pilots and skilled drivers are better than unskilled drivers. Induction is more convincing and easier to understand. We can easily understand the examples from our experiences in the world and most people can understand that kind of argument. Deduction, on the other hand, is stronger and is more useful against people who require the strongest kinds of argument.
Next, Aristotle discusses divides the topic of the tools to gain arguments.