The best comparison I can make is that it’s like your entire instant messaging (IM) history with someone.

我能提供的最合适的比喻是，它就像你和某个人之间即时通讯（IM）中的完整的历史记录。

youdao

Each set of sites must be given a unique instant messaging name to be accessible by IM, and the names are then added to the user's IM buddy list as aliases.

每一组网站必须被给予一个唯一的即时通讯名称，以使即时通讯工具能够访问，随后这些名字(以别名的形式)将被添加到用户即时通讯工具的好友列表中。

youdao

Meebo, for instance, has created a very large user base with their web-based meta instant messaging product (it enables you to use multiple IM services on the same webpage).

例如，Meebo已经通过它们基于web的meta及时通讯产品开发了相当大量的用户基础(它能够让你在同一个web页面上使用多个IM服务)。

youdao

It has a function on it that enables users to chat, much as they would over instant messaging (IM), but via television.

CNN: Home of future happening now

The interoperability issue among video carriers is somewhat similar in proprietary Instant Messaging systems, which also await unification among their providers so that someone on, say, Yahoo IM can talk to a Google Chat consumer.

FORBES: Worldwide Video Calling Gets Easier