Suspect Spans is a feature in Sentry's performance monitoring tool that helps developers quickly identify slow spans within transactions by surfacing a list of spans where the most time was spent. This feature, along with other tools like Operations Breakdown and Suspect Tags, provides a granular level of detail to help developers solve performance issues. By analyzing these features, developers can pinpoint the exact operations or "work" that are causing slow performance, allowing them to make targeted improvements to optimize their application's performance.