Boolean search is a way of building precise search queries by combining keywords with logical operators. AND narrows a search by requiring both terms, OR widens it by accepting either, and NOT excludes a term entirely, while quotation marks match an exact phrase. Recruiters have long used Boolean strings to dig through databases and search engines for candidates with a specific combination of skills.
Its strength is precision, and its weakness is that it is literal. A Boolean search matches the exact strings you type, so a search for JavaScript will miss a strong candidate who only wrote JS on their resume, and a search for one job title will miss someone whose company used a different word for the same role. Building a good Boolean string is a real skill, and even a good one is brittle.
Because of that brittleness, skill-aware search is increasingly taking its place. Rather than matching exact keywords, this kind of search understands that JS and JavaScript mean the same thing and that related titles describe the same work, and it ranks candidates by genuine fit rather than string overlap. Boolean search still has its uses, but it is no longer the only way to query a talent pool well.