Suspended 2nd chords
Suspended chords pull the third out entirely, so they land somewhere between major and minor rather than picking a side. Sus2 fills the gap with a major second sitting close to the root, which gives it an open, slightly hollow color. It's a favorite way to add movement to a strummed or arpeggiated part without changing the underlying harmony.
Other chord types
MajorMinorDiminishedAugmentedSuspended 4thDominant 7thMajor 7thMinor 7thMajor 6thMinor 6thMinor Major 7thDiminished 7thHalf-Diminished 7thAugmented 7thAdd9Dominant 9thMajor 9thMinor 9th6/9Dominant 11thMinor 11thDominant 13thMajor 13thMinor 13th7sus47b57b97#9Dominant 7#11Minor 6/99sus4Power Chord (5)Minor Add9Add117sus213sus4Minor Major 9thMajor 7#11Major 9#117b1313b913#117altAugmented Major 7thMinor 9b5Quartal (So What)