Stocks are often grouped up by the location of the companies that they represent. What this means is that the average investor may take a look at their portfolio and see which parts of the world they are invested in. Most people are pretty heavy on ownership of stocks within their native country, but it is often more helpful to spread the wealth around at least to some extent.  
Stock investments by location let an investor diversify his or her portfolio in such a way that an economic shock of some kind or another is not completely devastating to that portfolio in the long run. Today, investors can actually hyper-target their stock investments by location all the way down to particular countries that they wish to put their money to work in.  
There is a certain “king of the universe” feeling that may come with investing money in various parts of the world, but that is a good thing. One should work strongly to make sure their portfolio is well balanced and makes sense. There is little reason to work so hard at constructing the portfolio itself if one does not intend to build it into a diversified machine that works well in all conditions.  
Many people are highly thankful that they have spent time diversifying their portfolio when there is an economic shock of any kind in any part of the world. It is pretty easy to understand why. No one wishes to see their hard work and life savings go down the drain because they were too heavily concentrated in one area.  
The temptation to ploy money only into domestic investments is strong, but it is a temptation that must be avoided. There are far too many other options for a person to get involved with to waste money like this. Try to keep the money spread out and working at all times for you.