The three main types of real estate investment trusts, or REITs, in the United States are equity, mortgage and hybrid, according to Investopedia. Equity REITs invest in real property, while mortgage REITs invest not in property but in the underlying mortgages. Hybrid REITs own a combination of both.
Equity REITs typically earn revenue by leasing space in their owned property and through appreciation in property values, according to Investopedia. Mortgage REITs earn money by charging interest on the mortgages they hold. There are also more specific categories of REITs, such as timber REITS that hold mostly logging land, or retail REITs that invest mainly in shopping malls.