Path Markup Syntax provides a mini-language for describing complex collection of lines and curves. Make no mistake when describing it as mini-language – It is quite powerful and could reduces a lot of nested collection of Xaml elements into a single line.
Having said so, I personally favour the Xaml Element way of constructing elements, mainly due to readability factor. But the language is quite useful in its own ways.
Here is a little cheat sheet for Path Markup Syntax to aid your development cause.