Skype

Skype is an instant messaging app that runs on every platform (desktop or mobile, and on the web also). It supports real-time chats and calls (either audio or video), audio or video group calls and documents transfer.

Skype -- owned by Microsoft -- is available for iOS, Android, Windows and Mac, and offers video and audio calling, as well as a messaging feature. It has an easy-to-use interface, and supports up to 50 people on the same audio call (the number of video callers depends on what device you're using, according to the company). Skype also lets you record, save and share your video calls, and has live captions and subtitles. 

You can also actually use the app as you telephone, calling and texting phone numbers all around the world (different rates for different countries apply). They allow you to pay a monthly fee for minutes of free calls in the USA or worldwide, and they provide you also with a voicemail option. We have written an article on Skype alternatives, so feel free to check it out.

PROS

• Almost ubiquitous.
• Capable of phone calls around the world at a bargain price.

CONS

• On Windows the latest versions are bloated with ads.
• No emergency call.

Best for: real-time communications, voice services.

Skype for Business

Skype keeps the world talking. Say “hello” with an instant message, voice or video call – all for free*, no matter what device they use Skype on. Skype is available on phones, tablets, PCs, and Macs.

• Video calls – Don’t just hear the cheers, see them! Get together with 1 or 49 of your friends and family on a HD video call. Watch everyone’s smiles and cries when you tell them “We’re engaged!!!" 
• Chat – Reach people instantly. Send messages to your friends, grab someone’s attention with @ mentions, or create a group chat to plan a family reunion. 
• Share – Send photos and videos with your family and friends. Save shared photos and videos to your camera roll. Share your screen to make travel plans with friends or present designs to your team.
• Voice calls – Camera shy? Make voice calls to anyone in the world on Skype. You can also call mobile and landlines at low rates.
• Express yourself – Liven up conversations with emoticons, click on the “+” in chat to send a Giphy or images from the web, and annotate images with words, lines and more.

*Skype to Skype calls are free. Operator data charges may apply. We recommend using an unlimited data plan or WiFi connection.

Call landline and mobile phone numbers and send SMS messages anywhere in the world at affordable prices using Skype. Reach non-Skype users or contacts who are not online by choosing Skype Credit or Skype subscriptions. 
 
Choose Skype Credit as a pay-as-you-go option to call and SMS. If you call specific destinations, save even more with monthly subscriptions. Skype subscriptions are monthly calling plans that let you make unlimited, or fixed-minute calls to landlines (and mobiles where applicable). Subscriptions begin at $2.99 a month for US, and can vary by destination. To make an in-app purchase, open the app, go to the Call tab, and tap on the Skype to Phone banner. Skype Credit and Subscriptions purchased from the Skype app will be charged to your iTunes account when the purchase is confirmed.
 
Your account will be charged for Skype subscription renewal within 24-hours prior to the end of the current period. Your subscription is renewed automatically unless auto-renewal is turned off at least 24-hours before the end of the current period of subscription.
 
You can manage your subscription by going to your Apple ID account settings and choosing the auto-renewal option or turning it off any time after your purchase.