Noteflight is an online music notation software that allows users to create, view, and share sheet music. It offers a browser-based editor with playback capabilities, instrument selection, and collaborative features. Musicians can compose music, arrange scores, and export their creations in multiple formats like MIDI, MusicXML, and PDF. Noteflight is popular among composers, educators, and students for its user-friendly interface, versatility, and ability to collaborate on musical projects in real-time.