How Did Bartolomeu Dias contribute to the age of exploration?

I have a report to write on this, and I can't get a good answer anywhere on the net. Yes, I've googled it, but I must have a low vocab or something, but it's all too confusing, and I have to do this all on my own. Could you give me an understanding of who he was.. I know he did some trip to Africa or something... who was he? How did he help the "age of exploration" I need information that I can actually understand give me as big, but understandable explanation as i can get...Help?