This classification of mutual funds is more of an all-encompassing category that consists of funds that have proved to be popular but don't necessarily belong to the categories we've described so far. This type of mutual fund forgoes broad diversification to concentrate on a certain segment of the economy.
Sector funds are targeted at specific sectors of the economy such as financial, technology, health, etc. Sector funds are extremely volatile. There is a greater possibility of big gains, but you have to accept that your sector may tank.
Regional funds make it easier to focus on a specific area of the world. This may mean focusing on a region (say Latin America) or an individual country (for example, only Brazil). An advantage of these funds is that they make it easier to buy stock in foreign countries, which is otherwise difficult and expensive. Just like for sector funds, you have to accept the high risk of loss, which occurs if the region goes into a bad recession.
Socially-responsible funds (or ethical funds) invest only in companies that meet the criteria of certain guidelines or beliefs. Most socially responsible funds don't invest in industries such as tobacco, alcoholic beverages, weapons or nuclear power. The idea is to get a competitive performance while still maintaining a healthy conscience.