The purpose of audience research is to gather information from the target audience for a product to get more in depth analysis of what the audience is. There will be questions like age, gender, ethnic origin, county, income, job role, etc. This is just for the company to get a better understanding of what type of person buys their product.
The methods used to find a target audience are using qualitative and quantitative research. Qualitative research can find out the opinions and views on what the target audience think of the product ideas. Quantitative research is used to find data of previous products similar to it to improve and evolve, so the target audience will want to buy it. This will help out to find the target audience for the product.
The sources of information used to gather up a target audience would be seeing the reviews and ratings on previous products and looking on websites/YouTube to see what people had to say about that product. All the gathered information from this will help to find the target audience and create a questionnaire for them to see what they have to say about the evolving product.