If you’re setting up a Standard/Managed account, the Parental Controls feature affords you the opportunity to shield your Mac—or its very young, very fearful, or very mischievous operator—from confusion and harm. This set of options, newly beefed up in El Capitan, is helpful to remember when you’re setting up accounts for students, young children, or easily intimidated adults. (This checkbox is available for Admin accounts, too, but turning it on produces a “Silly rabbit—this is for kids!” sort of message.)
You can specify how many hours a day each person is allowed to use the Mac, and declare certain hours (like sleeping hours) off-limits. You can specify exactly who your kids are allowed to communicate with via email (if they use Mail) and instant messaging (if they use Messages), what websites they can visit (if they use Safari), what programs they’re allowed to use, and even what words they can look up in the OS X Dictionary.