A filled circle means "or equal to" in which this case the symbol is less than or equal to, making the dot filled. Since 2 is greater than x, the line would start on the two and continue farther down the line to show that anything 2 or greater is more than x.
Yes, some of these theorems include Side and side, angle side angle, and side side side. For right triangles, there's hypotnuse angle, leg angle, leg leg, and hypotnuse leg.
