Apps (short for applications) are software programs that need to be installed on a device in order to work. They can be found by visiting online stores such as Apple's App Store, Amazon or Google's Play store.
Apps are operating system-specific, so one app has to be built for the Android operating system, a different app has to be built for Apple devices, a different app for BlackBerry phones etc.
Websites on the other hand can be viewed by any device, running any operating system and any browswer which makes them available to a much wider audience.
Websites need an Internet connection to be used but apps can be used offline. Apps may also access data from the Internet to keep them updated. Games don't usually require an Internet connection but maps for example might.
Apps are much higher maintenance, requiring regular updates to work on devices but websites are low maintenance and don't require updating. Apps can be deleted from the device by the user but websites are always available.
If you run a business, you really should have a website without a doubt. Even if your organisation doesn't sell anything, people expect to be able to view a supporting website just to view basic information and as a point of contact. Conversely, not all businesses neccessarily need an app.
Apps, unlike websites however can take advantage of device hardware. For example an app can utilise a phone or tablet's built-in GPS to add mapping and direction functionality. This would be useful for things like taxi services, restaurants that do deliveries or fitness and training programmes which could monitor how far a user jogs each day.
Other handset features that the app could utilise include: camera, phone calls, text messaging, clock, alarm, touch screen and accelerometer (which measures how fast the device is moving - Think sat nav apps).
You might decide to get an app if you're developing a game for example which could be purchased from the app store, downloaded and played offline, or a product that requires a lot of personalisation such as note taking or productivity tools such as a to-do list reminder or a photo editing tool.
If you'd like an app for your business, you can receive quotations from up to four leading app design companies by completing one simple form.