Dilemma! modern trading complexity

So I have read about how the modern market is complex and fragmented. What does it mean that the market is fragmented? Also, if it's harder for any one exchange to see the full picture and take action, can bloomberg create something to display the full picture?

I'm sorry if this sounds like a dumb question, but I'm just getting into finance and I would really like to learn. Thanks in advance.

“This is the sort of situation that has been a worry for a long time, but the markets have changed in a way that has made things more difficult,” said Robert L. D. Colby, former deputy director of trading and markets at the S.E.C. “They’ve become more fragmented, so it’s harder for any one exchange to see the full picture and take action.”