If you're on this page, I assume you have some interest in astronomy. If so, get a phone app like SkySafari. You'll learn more about the sky from this app than almost any other resource. Get one now.
There are programs for your desktop as well. I've stopped using mine since I seldom bring my desktop outside under the stars. And the mobile apps allow you do most of the desktop functions plus a whole lot more (like identifying what you're pointing your phone at).
Desktop Apps can provide utility that Mobile Apps cannot, especially integration with other workflows, be it detailed observing session planning, astrophotography contol, or documentation.
StarryNight is a robust software package for the desktop, but it's based on the desktop pricing model: it's expensive compared to phone apps.
Stellarium from Stellarium.org is a free Desktop Planetarium app. Very capable. It has a web version and mobile versions.
Mobile Apps
There are some free apps and Google has a free Google Sky app, but I'll talk about SkySafari, since it's the primary planetarium app I see used most broadly on phones and tables (there are many desktop programs, including Starry Night and many observation planning products). SkySafari has a basic (but vary capable version) for as low as $2.99. Other versions can even run GoTo Telescopes.
SkySafari running on a modern cell phone or table will show a map of the sky as you hold it up to the sky. Point the phone/table to a different part of the sky, the map follows. It's a great way to learn the sky.
Planetarium App Guidance
Many new telescope computers have built-in WiFi specifically to interface with planetarium apps so that you don't have to rely on their Hand Controllers. Others work with WiFi adapters to connect with your phone, tablet or computer.
Hand-held, character-based menu navigators are obsolete; immersive, telescope-tracking sky map navigation is the future.
If a picture is worth a thousand words, then look at this picture below and answer this question:
which interface is more intuitive?
AstroDevices.com offers a WiFI adapter for interface with scopes that have encoders (many mounts have kits to add encoders).
I've had good luck with their inexpensive Nexus II adapater and their more complete Nexus DSC.
Below is a video (poorly shot with my phone, sorry) demonstrating SkySafari on iPad navigating a Meade Lightbridge 12 via the Nexus.
AstroDevices offers a full computer-plus-wifi Nexus DSC. It's more expensive, but it's a far more robust solution, eliminating the need for a standalong computer (like SkyCommander, ArgoNavis, etc.). I like the interface quite a bit more than most handheld computers. I don't need a manual to know how to use (the last thing you want to do in the dark is have to read a manual). It turned my Obsession/ServoCAT/ArgoNavis/SkySari system from something torturous to use to something fun again.