Circles, squares and diamonds designate the degree of difficulty of slopes and trails at a ski resort. True beginners should stick with circles. You will have WAY more fun if you progress incrementally. More experienced skiers and snowboarders should also pay attention to designations.
Here is a quick explanation on how the trail signs are determined.
In general, approximately 25 percent of the trails are designated green, about 50 percent are blue, and about 25 percent are black. If a mountain is steep all over, the green-circle trails can be a challenge for novices. They are the easiest trails at that resort, but they may be tough for someone who is learning. (Image via Mountain High)
A few resorts use the symbols in combination to show even more degrees of difficulty. Here is an example:
Some resorts use additional designations: a green circle, blue square, black diamond inside a blue square, black diamond and double black diamond.
The designation for half pipes and freestyle terrain parks looks like this:
Pick up a trail map at the ticket window to find out right away how trails are ranked. Signage on each trail also will include the designation. Trying the easiest slopes first gives you a good feel for how trails are ranked. Especially for beginners, easiest designations offer a chance to warm up and determine the relative degree of difficulty at that area.