WeChat is an application that allows users to communicate through different mediums. They currently are available on multiple platforms: iOS, Android, Blackberry, Windows, Nokia and any web browser.  WeChat is created by Tencent Holdings Limited, a listed technology company based in Shenzhen. It was launched in January 2011 and has surpassed 100 million users by March 2012, outpacing Facebook and Twitter.  Now it has around 400 million active users. 
- Push to Talk
Users can push to talk to send a voice message. Sending a voice message allows the person to have a more personal connection by giving out more social cues like tone, volume of the voice. The maximum length of a voice message is 59 seconds. The user can click on the voice message to and decided whether to listen to it on "handset mode" (by holding the phone as if you are calling someone) or on "speakerphone mode" (by pressing the voice message). If one made a mistake while recording a voice message, one could easily swipe up and delete what one just recorded. This is a popular function of WeChat and is a main reason how WeChat became so popular.
This is similar to Instagram, with users sharing pictures to a private group of friends. In addition to pictures, you could also share statuses and Web links. The main difference between WeChat's moments and Instagram is that you can only see the "likes" and "comments" by your friends. Only the user could see the total count of likes and the comments. This makes "moments" more privatised.
- Video Call
Similar to Facetime, WeChat also has its video chat function. The advantage of using WeChat over Facetime is that one could video across different mobile platforms.  For example, an iPhone user could video chat an Android user.
- Walkie Talkie
One could start a "walkie talkie" session with other pals or within a group. Anyone who joins could hear the other person speak when the button is pushed down.
- Drift Bottle
One could throw a virtual "bottle", containing either a voice message or a text message, into the "ocean". Some person (could be other side of the world) could go into the "ocean" and collect this bottle. This person could then choose to ignore or reply.
Ways to add WeChat contacts
1. Mobile Contact If your friend's mobile number is bridged with his/hers WeChat account, one could automatically see him/her in the contact list and could decided whether to add him/her.
2. QR Code Scan Every account has its own QR code and a after a simple scan a user could add a new pal.
3. WeChat ID If the person has a WeChat ID then one could search for him.
4. Radar If the person is within a 1 km, Radar allows them to find each to other if they are pressing the "radar" button. This could also be done within a big group.
WeChat combined the functions of SMS, Facebook, Instagram and Skype. Tencent has invested a lot of money into global expansion since 90% of its users are still based in Mainland China.
- WeChat Launch event in India
- Direct source from Tencent company.