According to a book I'm reading for class (The Human Web, McNeill & McNeill) Arabic numerals became important in Europe during the 11th century. The authors say that the number zero became important and place value numeration.
Could someone expand on this and explain how the arabic numerals were different and possibly better than the old system?
It's not about numerals themselves, but about the numerical system they were used in. Place value numeration (or, positional system) was more efficient for use in arithmetics. Especially for bookkeeping.
Roman numerals were used in a cumulative-additive system in which each power of base was represented by a different numeral. For example, MMXIV reads as 1000+1000+10+(5-1). Arabic numerals (and, critically, zero) were introduced with positional system in which the power of base is encoded in the numeral's position in the number, so 2014 reads as 2x1000+0x100+1x10+4x1. Even though calculations with Roman numerals were doable, it's easy to see why any calculations past addition would be much more efficient with a positional system — and, critically, would require much less training — than those with the Roman additive one.
This is an extremely simplified overview. There have been more, even weirder numerical systems in use in Europe over time, and the transition wasn't as fluid as one might expect. There even was a semi-positional system with Roman numerals around for a while. There's likely more information about the different systems and their history than you could wish for in Stephen Chrisomalis' Numerical Notation: A Comparative History (Cambridge, 2010).