Via The Wall Street Journal, a definition of “frontier” markets:

Most investors know about emerging markets like Mexico or Brazil. Lesser known are the so-called frontier markets such as Argentina, Pakistan, Botswana, Ukraine and Vietnam.

As far as economic development, frontier markets are at the bottom of the heap, says Win Thin, global head of emerging markets at Brown Brothers Harriman in New York. “Typically they are poorer countries, but they are on the way up.”

As frontier economies grow, they may become emerging markets and then eventually developed markets like the U.K. or France.

For investors, which countries are considered frontiers varies with whom you ask. MSCI has 24 countries in its Frontier index, while S&P Dow Jones Indices has 34. Both have a good amount from Africa.

“The attractiveness is that these countries could grow very quickly,” says Mr. Thin. Some investors who “missed the boat” in other hot markets, he says, might have another chance in frontiers. But there are risks: There isn’t much liquidity in the local markets. “It’s easy to get into an investment, but could be impossible to get out if the markets turn against you,” says Mr. Thin.

For individual investors, mutual funds and exchange-traded funds are likely the best bet. Portfolio managers suggest only a small allocation to frontier stocks: in a range of 6% of a portfolio to 10% for more-aggressive investors. The iShares MSCI Frontier 100 (FM) or Templeton Frontier Markets (TFMAX) might be suitable, although there are many other products.