Complex sentence: Hooking up is unique for when and why the sexual encounter occurs: instead of building a relationship before initiating sexual acts (from kissing to intercourse), hooking up allows the participants to become intimate without the expectation of commitment.
Split into simpler sentences: Hooking up is unique for when and why the sexual encounter occurs. Instead of building a relationship before initiating sexual acts (from kissing to intercourse), hooking up allows the participants to become intimate without the expectation of commitment.