A pathfinder is a bibliography created to help begin research in a particular topic or subject area. Pathfinders are also called subject guides, topic guides, research guides, libguides, information portals, resource lists or study guides. Pathfinders produced by the Library of Congress are known as "tracer bullets". What is special about a pathfinder is that it only refers to the information in a specific location, i.e. the shelves of a local library.

According to the Online Dictionary for Library and Information Science, a pathfinder is "designed to lead the user through the process of researching a specific topic, or any topic in a given field or discipline, usually in a systematic, step-by-step way, making use of the best finding tools the library has to offer. Pathfinders may be printed or available online."

The goal of a pathfinder is to gather the most useful, relevant, reliable and authoritative resources on a variety of academic, work-related or general-interest topics. Originally provided in print format in the 20th century in large academic libraries, pathfinders have evolved with the emergence of the World Wide Web and may now act as portals to information about resources in a variety of formats, including books, encyclopedias, bibliographic databases, almanacs, documentaries, websites, search engines and journals.

Often used as curriculum tools for bibliographic instruction, the guides help library users find materials or help those unfamiliar with a discipline understand the key sources."

Pathfinders are intended to be a launch point for research on a particular topic, via the collection of select materials available in a particular institution on that topic. However they are not generally an exhaustive collection of all of the materials on a given topic- they are designed for beginners in research to find the fundamental information they need to get started. In addition to this basic concept, many research guides include other complex goals, such as "teaching how to complete a given task, providing access to tools for actually doing it, promoting collections and services, educating users about the research process, and providing disciplinary context for in-depth research needs". Pathfinders also help to teach essential information and technology skills, and promote books and reading. They are broader in scope than subject headings, and have been chosen from university course descriptions, thesis titles, and from term paper titles. Breaking down the topic the pathfinder is about is recommended to reduce the cognitive load for users. For public libraries, it has been suggested to use surveys, past experience and hot topics from local media to find topics for pathfinders. It has been argued to expand the purpose of a research guide from being a list of resources to also incorporating instruction on information literacy, both in 1984 and 2014.

MIT pathfinders in the 1970s had the following format:

Although the format varied, it emphasised subjects that were broad in scope and providing many different types of sources to the reader. In contrast, some academic libraries created specific pathfinders that functioned as a partial bibliography. Jackson rejected the bibliographic format in 1984, arguing that search strategies should be taught in a pathfinder. In 2012, a study on mental models of research guides showed that students preferred guides which were format-agnostic rather than grouped by format type. In 1995, Jim Kapoun argued that key features of good pathfinders were "compactness and basic informational resources". Browser extensions like alternative search plugins have been added to subject guides.

Booklists have been produced by libraries since at least the 1950s. Patricia Knapp, in the 1960s, integrated librarianship with academic instruction, but the term pathfinder was coined in 1972 by Marie Canfield. From approximately 1973-1975, the Model Library Program sold pathfinders among libraries, but there was not enough interest to continue selling pathfinders, as most libraries preferred to create their own. However, this was an expensive proposition, as collection-tailored pathfinders took about 8 - 20 hours of librarians' time as of the 1980s.