What does square bracket [] mean in the below code?

Question

I got below code from http://msdn.microsoft.com/en-us/library/dd584174(office.11).aspx for adding custom property in webpart tool pane. What does square bracket ([]

Answer 1

They're called attributes.

Here's a quick example of how they can be used: http://www.codeproject.com/KB/cs/attributes.aspx