In its most common sense, methodology is the study of research methods. However, the term can also refer to the methods themselves or to the philosophical discussion of associated background assumptions. A method is a structured procedure for bringing about a certain goal. In the context of research, this goal is usually to discover new knowledge or to verify pre-existing knowledge claims. This normally involves various steps, like choosing a sample, collecting data from this sample, and interpreting this data. The study of methods involves a detailed description and analysis of these processes. It includes evaluative aspects by comparing different methods to assess their advantages and disadvantages relative to different research goals and situations. This way, a methodology can help make the research process efficient and reliable by guiding researchers on which method to employ at each step. These descriptions and evaluations of methods often depend on philosophical background assumptions. The assumptions are about issues like how the studied phenomena are to be conceptualized, what constitutes evidence for or against them, and what the general goal of research is. When understood in the widest sense, methodology also includes the discussion of these more abstract issues.

The most discussed distinction among types of methodologies is between the quantitative and the qualitative approach. Quantitative research is the main methodology of the natural sciences. It uses precise numerical measurements, usually with the goal of finding universal laws that can be utilized to make predictions about future events. Qualitative research is more characteristic of the social sciences and gives less prominence to exact numerical measurements. It is often concerned with human behavior and experience. It aims more at an in-depth understanding of the meaning of the studied phenomena and less at universal and predictive laws. The sample size in qualitative research is usually small in comparison to quantitative research. Many discussions in methodology concern the question of whether the quantitative approach is superior, especially whether it is adequate when applied to the social domain. In recent decades, many social scientists have started using mixed-methods research, which combines both methodologies. Another classification distinguishes between substantive and formal methodologies. Important in this regard is whether the research seeks particular insights in one specific area or more general insights governing many different fields. The methodological outlook known as "proceduralism" is controversial and holds that the goal of methodology is to precisely codify rules that automatically lead to good research if followed exactly, similar to a recipe.

Many theorists have argued that methodology is important for various issues. For example, a proper understanding of it may help researchers arrive at reliable theories in an efficient manner. In some cases, the same factual material can even lead to very different conclusions depending on the chosen methodology. Interest in methodology has risen significantly in the 20th century. One reason for this may be that many global problems faced by contemporary society can only be solved through interdisciplinary work. Methodological advances aid such collaborative efforts by making it easier for researchers from one field to understand how their peers from another field arrive at knowledge. Nonetheless, many criticisms of methodology have also been voiced. Many objections are directed at specific methodological outlooks, for example, at outlooks that give primacy to quantitative research. A few criticisms are more wide-ranging in that they reject methodology as a discipline in general. In this regard, some critics hold that it is useless based on the claim that what matters is the usage of methods but not studying them. More severe criticisms see methodology as harmful, for example, because reflection on methods may lead to more mistakes than blindly following them or because the focus on method restricts the freedom and creativity of researchers.

Methodology is relevant to various fields. The dominant methodology in the natural sciences is called the scientific method. It includes steps like observation, the formulation of a hypothesis, conducting an experiment designed for this specific hypothesis, comparing the measurements to the expected results, and publishing these findings. Common methods found in the social sciences are surveys, interviews, focus groups, and the nominal group technique. Surveys usually involve a large sample size and use questionnaires with closed questions. Interviews normally include some open questions. For structured interviews, all questions are pre-planned while unstructured interviews require the moderator to improvise and ask unplanned questions based on the flow of the interview. Focus groups involve a group interview of a small number of demographically similar people and usually include open discussions as well. The nominal group technique is a slight variation of focus groups that organizes the group exchange in a more structured manner. This helps to minimize certain group effects that may influence how the participants respond. Philosophical methodology belongs to metaphilosophy and discusses methods like methodological skepticism, the phenomenological method, conceptual analysis, and thought experiments. In mathematics, synthetic methods proceed from the known to the unknown while analytic methods trace a path from the unknown to the known. Statistics is concerned with methods used to analyze, interpret, and present data.