You may have noticed your Mac alerting you that a new download is available. Maybe, instead of downloading it straightaway, you just keep putting it off for later. This is a bad idea for two reasons. First, you’re leaving your computer more vulnerable to getting hacked. Second, you’re missing out on some awesome new features in Apple’s latest desktop version, OS X El Capitan.El Capitan, named for an iconic rock formation in Yosemite National Park, isn’t a huge update to the Mac. If you like your computer just the way it is, rest assured that El Capitan brings nothing jarring that will unnecessarily shake up your well-honed workflow. However, what it does do is refine and streamline the updates Apple made in last year’s OS X update, Yosemite — and add some nifty tools, too.For example, while it’s always been easy to store information on your computer, finding it again can be a pain, so El Capitan has several features that make that process less of a headache. And if you ever lose track of your mouse pointer’s position on-screen (especially problematic on a big new Retina-display 27-inch iMac or a Cinema Display), shaking the mouse momentarily enlarges the on-screen pointer so you can find it in a snap. It's dorky, but useful.A lot of the updates will feel familiar if you’ve already updated your phone to iOS 9. So if you haven’t yet gone the distance to OS X 10.11 (or even if you have), here’s what you need to know about what’s new and different.