It is possible to use an omniscient viewpoint where the reader is able to know what every character is thinking or feeling, and is written in third person only. If the reader is only allowed to know what the characters do and say—not what they feel—it is called the Reportorial viewpoint.
Many books are written from the viewpoint of only one character, and in that case the reader is privy to everything they need to know about that character. Although often written in first person, it can also be done in third person.
In some cases, the author will have different chapters written from the viewpoint of any number of different characters in the story. However, some will contend that doing so keeps the reader from identifying most closely with the intended protagonist. The author must decide which approach is going to be the most effective for the story they want to write. Some will even try writing the story from a number of different viewpoints in order to decide which will be most effective in each case. All that being said, the reality is that many very successful authors do change viewpoint in the middle of a scene, but it's not recommended that you do so until you are a very successful author. For help on picking the right viewpoint character, go to: http://www.fictionfactor.com/articles/viewpoint.html.
For more on viewpoint, go to: http://www.writingforward.com/news-announcements/guest-posts/5-ways-to-use-narrative-viewpoint-in-fiction-writing.