What is enterprise software, exactly?

Question

I don't understand the difference between "normal" software and enterprise software. Even after reading these...

• "Enterprise Software" on Wikipedia
• "Enterprise Software Is Sexy Again" on Techcrunch
• "The Great Enterprise Software Swindle" on Coding Horror

I can't really wrap my head around the real differences. Is there any difference at all between the two? Why do people say enterprise software sucks?