Google Plus has several options when it comes to making contact with other Google Plus users. You can send a private message to a friend by creating a status update and setting it so that it only publishes on your friend's stream. But if you want more immediate, two-way communication you still have some interesting options.
Like Gmail, Google Plus incorporates the Google Talk network directly into the Google Plus service. This lets you send and receive instant messages through Google Talk. A history of your chat sessions through Google Talk exists on your Gmail account. You can also access Google Talk through its own dedicated instant messaging client or one of dozens of third-party clients like Pidgin and Digsby.
A second way to get in touch with up to nine other Google Plus users is a hangout. A hangout is a video chat session. To participate in a hangout, you'll need a webcam and a microphone. Headphones also come in handy since they cut down on echo. You can have a public hangout, limit hangouts to specific circles or even keep it restricted to specific users. Whichever route you choose, you'll be limited to 10 participants total, including yourself.
Once a hangout begins, you'll see a live video window for each participant. Whoever is speaking at any given time will take center stage and have a video window larger than everyone else. As soon as someone else begins to talk, the view will switch and that person will take the focus. If two or more people are talking at once, Google Plus will display whoever is the loudest.
How does Google Plus do this? Each person in a hangout has his or her own video and audio feeds streaming into the service. When Google Plus detects audio from one of the feeds, it switches the view to that person. For multiple audio feeds, Google Plus simply analyzes the amplitude of the sound waves coming in to the system -- we perceive sound wave amplitude as volume.
Once in a hangout, you can chat or even start a YouTube viewing party. People in the chat room can pick from YouTube clips and display them on the screen. At that point, a hangout may turn into an amateur version of "Mystery Science Theater 3000" or "RiffTrax" as users provide commentary to video clips.
A third way to communicate with other Google Plus mobile users is a huddle. With a huddle, you send out text messages to a specific group of people. Each person needs to have the mobile version of Google Plus installed on a smartphone. Then, you add the people you want to communicate with to the huddle. When you send out a message to the huddle, it goes to each person you've added to the group. Each recipient can respond to the message, which also goes out to the whole group. It turns text messaging into a party chat system. While communication may be asynchronous, meaning not everyone is actively chatting at the same time, it helps keep each member of the group appraised of what is going on.
It's easier to understand with an example. Suppose you want to go see a movie and you'd like to invite several friends. You add each of the people you'd like to show up to a huddle and suggest the movie. Each person can then respond to the whole group and turn it into a conversation. This can help narrow down the time and place you'll go to catch the latest flick.
Huddles resemble other messaging services like Twitter and Beluga. Since building a huddle depends upon your friends owning a mobile device capable of running a Google Plus app, it may not work out for everyone.
Next, we'll look at how Google Plus handles privacy.