The December 12th Instagram event has just wrapped and as had been rumored, they will be adding messaging to the service. This is being introduced as Instagram Direct and it will allow users to send image and video messages to friends. While there is more to this, there was some comparison to days of old and sitting around a box of photos and having a conversation.
Instagram Direct sort of takes that concept into the present day. That being said, this is arriving as the v5.0 update and it will be available by way of the Google Play Store a bit later today. During the announcement we learned how users will be able to send these messages to one person and up to 15 people in total and about how the process begins by tapping the "Send to One" button.
Once the message has been sent a return to that image will show (underneath the pic), the profile image for yourself as well as the person(s) the image was sent to. This is where the read receipts come into play. The profile pic of the recipients will initially be faded out. They will then come to full color after the person sees the message. Furthermore, a check mark will appear when they view and a heart will appear if they like.
Aside from simply viewing and liking the image, the conversation takes place below the image. You will be able to chat back and forth between the person or persons that you sent the message to. These messages were referred to as "Moments" during the announcement and they will all live in your inbox. They can also be re-visited later. And users will get a notification of new messages in the upper right corner of the Instagram app.
Basically, Instagram Direct is about having a conversation around an image. There is one important aspect here -- your Instagram inbox is not going to be spammed and overflowing. Instagram has this set so anyone can send anyone an image, however you will only receive inbox notifications from those you follow. Hence, no overflowing inbox of message spam. Otherwise, any new messages from those you don't follow will show up in the pending request section of the app.
SOURCE: Instagram Blog