A hold harmless clause (also called an indemnification clause; the two are often used interchangeably though there are technical distinctions) is a contract provision in which one party (the indemnitor) agrees to absorb liability for claims that would otherwise fall on the other party (the indemnitee). Construction contracts almost always include hold-harmless provisions running from contractor to owner and from sub to GC.
Three common types: limited (indemnitor only covers claims arising from their own negligence), intermediate (indemnitor covers claims arising from joint negligence), and broad-form (indemnitor covers all claims regardless of fault). Many states have anti-indemnity statutes that limit or void broad-form indemnification in construction contracts. Always review hold-harmless language with a construction attorney before signing.