Well, I'm actually not very clear on what happens once you have the visa. I think when you make use of your visa, that is the point where people say that you have 'landed'. Once you landed I believe that your are free to go traveling, as long as you reside in Canada. I don't know if you must stay in Canada without leaving at all for a certain period of time after landing.
Your permanent resident status allows you to live in Canada, but there is also a time limit on how long you can live outside the country. To keep your status as a permanent resident, you must live in Canada for at least two years within a five-year period.
Once you land you can indeed go back home to your country of residence but to maintain PR you need to be here at least 2 out of every 5 years.