4) Global funds
This category is extremely diverse. Some global funds can be categorised as sector funds that scout for stocks globally. For example, a gold fund would invest in gold mining stocks across the globe. In a similar vein you have funds focused on stocks in specific areas - mining, commodities, agriculture and energy.
There could be funds focused on a particular geography such as Europe, Asia, Brazil, China, Japan or the U.S. They could also be thematic by looking at emerging markets.
Approach such funds the way you would approach a sector fund. Be convinced of why you want exposure to such a sector or geography or theme. Let this be a non-core holding in your portfolio.