High ratio shortening is "purer", as it has no added water or salt, and has micro-emulsifiers that allow you product to hold more sugar and liquid compared to Crisco shortening or shortening that you find at the grocery store. High ratio can only be found in cake supply stores or specialty stores at this time. High ratio shortening used in an icing recipe (instead of Crisco or butter or along with butter) allows you to create a fluffy, stabilized icing that is not greasy and holds up better than butter than Crisco. High ratio shortening has no after taste and does not break down like Crisco does, as Crisco has added water and salt (and the butter version has added color). There are several brands of high ratio shortening on the market, which include Alpine, Sweetex, and Ventura. All brands are quality brands. In many States you may still find high ratio shortening containing trans-fat (which creates a creamier icing). If you happen to live in the State of California, then you are only able to purchase trans-fat free high ratio shortening. (Any store/retailer/wholesaler in California, will be fined $250 if caught selling shortening containing trans-fat.) 

Be aware that over-mixing or over-beating will cause the shortening to become grainy, thus your icing will be grainy. Also, do not store shortening in the refrigerator. It should be stored in a cool, dry place. Trans-fat free high ratio shortening tends to have a 'harder' consistency in the container (much like butter when you buy in a bar). It is suggested that you combine some of your liquid in a bowl with your shortening and mix slowly with a fork. Add all of your dry ingredients to the mixing bowl, and while mixing add in some liquid, then the shortening, then the rest of the liquid to the consistency you desire. Keep your mixer on low.

For stabilized versions of cream cheese icing, I use 1/2 C cream cheese and 1/2 C high ratio shortening. Same with stabilized butter cream...I use 1/2 C unsalted butter and 1/2 C high ratio shortening. You can even substitute Mascarpone for cream cheese. 

Regardless, do not get frustrated. Experiment too! You never know what you might create!

Questions? Feel free to ask the question in the comment section, and I will answer it!