Split Core Transformers vs. Ordinary Transformers

Greeting all,
I was reading one datasheet regarding to split core transformer. In data sheet in the feature of split core is written like this

"This split-core current transformer was designed for easy installation on large bus or
wire conductors in order to make electrical load surveys or for continuous monitoring of
current."

Here is the link.
http://www.flex-core.com/split-core-...ansformers.htm

I have two questions regarding this.

1- what is the difference between the ordinary CTs and split core CTs?
2- Is really designed only for easy installation on large bus or it has any other special feature that ordinary CTs doesnt.