For years, people installed software onto their computers by buying disks: floppies, CDs, and, later, DVDs.
But starting with the iPhone, people installed software onto their phones by downloading it directly from the Internet. Once everybody saw how convenient (and profitable) that system was, it didn’t take Apple long to realize it could bring the same convenience to the Mac.
So now there’s the Mac App Store—or, as the program is called in your Applications folder, just App Store (Figure 6-1). It’s an online catalog of software from huge software companies, tiny one-person software companies, and everything in between. You can read about the programs, check out customer reviews, and download them directly to your Mac. (As you probably know, Sierra itself is an App Store download.)
Figure 6-1. Top: Mastering the App Store won’t take you long; just about everything you need is in the toolbar at the top, including a search box and buttons like Featured, Top Charts, and Categories, which are meant to help you dive into the catalog of Mac software. The remaining tab, Purchased, shows everything you’ve ever bought using your Apple account, for easy re-downloading.
There are some huge advantages to this system. Since there’s no box, disc, registration card, shipping, or stocking, the software can cost a lot less; Apple’s own programs certainly reflect this price advantage. Plenty of programs in the App Store are actually free.
Furthermore, Apple controls the transaction on both ends—it knows who you are—so there are no serial numbers to type in. The installation no longer interrupts you with warnings like “Please enter your password to install this software” or “This software appears to have been downloaded from the Internet.” Once you click Buy, the software downloads and installs itself automatically, without any interaction from you.
And there are no discs to store and hunt down later. If you ever get a new Mac, or if you ever need to reinstall a program from the App Store, you just re-download it from the Purchases tab; the App Store remembers that you’re a legitimate owner. Better yet, you’ll be downloading the latest version of that program; you won’t have to install all the “.01” patches that have come along since.
Tip
To hide an app you’ve bought so it no longer appears in Purchased, right-click its icon and choose Hide Purchase. (To unhide it later, click the Account link on the main page of the App Store; under the “iTunes in the Cloud” heading, choose View Hidden Purchases.)
And speaking of updates: Since Apple knows what programs you have, it can let you know when new versions are available. And it does: A numbered badge appears next to the 
→App Store command. The updates are small files, so they download quickly; the App Store delivers only the pieces that have actually changed.
Some details:
You can opt to have new versions of your programs quietly and automatically downloaded and installed in the background, so you’re never bugged about their arrival. (Open System Preferences→App Store. “Download newly available updates in the background” downloads new versions but asks your permission before installing them. “Install app updates” goes the next step and installs them without consulting you further.)
“Automatically download apps purchased on other Macs” (also in System Preferences→App Store) ensures that when you download an app on one Mac, it auto-downloads on all your other ones, too (assuming they’re logged in with the same iCloud account). Handy, really.
If the App Store app indicates that new versions of your programs are available, then click the drop-down menu next to the Update All button. There, for your time-shifting pleasure, is a shortcut menu containing options like Install Now, Try in an Hour, Try Tonight, and Remind Me Tomorrow. The point is to set up a downloading session for a time when (a) you’re in a Wi-Fi hotspot or (b) you’re asleep and those big downloads won’t slow down anybody’s Internet work.
One final advantage of the App Store concept: If you decide to use Launchpad, described starting in Tip, then anything you’ve bought from the App Store is easy to delete with a single click.
In general, the App Store works exactly like the iPhone/iPad App Store. Click a program’s icon to open its details page. Here you’ll find reviews and ratings from other people, a description, pictures (screenshots) of the program, and much more information to help you make a good buying decision. See Figure 6-1 for more details.
When you buy an app, Launchpad opens automatically, so you can see where it went.