Qualitative studies are based on collecting information that describes people's perspectives and motivations. Unlike quantitative studies, they do not try to quantify anything or use statistics.
A qualitative study might use focus groups, or interviews or observation, or a combination of methods. Sample sizes (the number of people recruited to take part) are more difficult to predict, and are often smaller than in quantitative studies. Qualitative researchers will often analyse their data as they go along, and stop looking for new people to take part when no new insights are being found.
Qualitative researchers do not assume that they know what the important issues are. Often it is not until the research is underway that the real issues are identified. Therefore, qualitative methods are general designed to give participants the freedom to raise issues that are important to them. For example, topic guides will be developed for interviews rather than tightly defined questionnaires.
Qualitative methods are often used in combination with other methods to provide rich and comprehensive data sets.