Superscore means colleges take your highest score from each test section, and combine those high scores from different test dates into a highest-possible composite score.
Score Choice means you can decide which SAT scores to send and which not to send. With Score Choice, if you choose to send SAT scores from a certain test date, you can't pick and choose which sections to send - it's all or nothing. You'll have a choice of which test dates you want to send in the case of the regular SAT and your choice of which individual tests you want to send in the case of SAT subject tests.