NEW YORK (TheStreet) -- Interest has been growing in so-called smart beta funds over the last several years, says Tony Davidow, asset allocation strategist for CharlesSchwab (SCHW) - Get Report. 

These increasingly complex funds are nothing new, but they have become more mainstream in recent years. Essentially, these are funds that use non-traditional weighting metrics and different strategies. 

For instance, smart beta can be momentum or low volatility funds, Davidow said, adding that equal weighting is also popular. When equal weighting a fund, the same amount of emphasis is put on each holding rather than the more traditional weighting of putting more emphasis on the larger companies. 

This makes the fund more attractive in some instances because the overall performance isn't as directly tied to the performance of only a handful of stocks, Davidow explained. 

Charles Schwab SCHW data by YCharts

So should investors replace all of their tradition index fund exposure with smart beta? "There's a role for both," he said. 

Sometimes traditional index funds will outperform and at other times smart beta funds will be the winner. So having some combination of the two will create a more "durable portfolio," Davidow said. 

However, investors really should understand what they're buying before allocating money to smart beta, he said. Thanks to the categorization of these funds it makes it much easier for investors distinguish among them. This is vital, since not all funds "are created equal."