Google Scholar applies Google's search technology to academic literature. It indexes journal articles, conference papers, theses, books, preprints, and patents across virtually every discipline. Search results include citation counts, links to full text where available, and tools to find related papers. You can set up alerts for new work in your field, follow specific authors, and track who is citing your own publications.

What makes it useful is the breadth. It pulls from publisher websites, university repositories, and preprint servers in one place. There's no curation or filtering by peer-review status, so you need to evaluate sources yourself, but for finding an obscure paper or checking citation counts before writing a literature review, it's hard to beat. Many researchers make it their first stop.