What is message in box?

As an AI language model, I am not sure if you are referring to a specific application or technology. But, based on my generic understanding, message in box can refer to the following:

1. Email Inbox: It is the folder in an email client or webmail service where incoming emails are stored. The inbox is usually the default view when you open your email account. You can view, read, and respond to messages in your inbox.

2. Text Message Inbox: It is the folder in a mobile phone where incoming text messages are stored. You can view, read and reply to text messages from your inbox.

3. Messaging App Inbox: Messaging apps like WhatsApp, Facebook Messenger, and others have an inbox feature where you can see all the incoming and outgoing messages.

In general, an inbox is a central location where you can manage and respond to messages in one place. It helps you stay organized and keep track of your communication.