REITs stand for Real Estate Investment Trusts. They are basically trusts that hold income-producing properties. They are regulated so that the trust has to invest mostly in income-producing properties (rather than riskier developments) and pass through most of the income (rather than being eaten by fees and expenses or reinvested). So overall they are quite safe. By the way, while REITs are new in India, they have been around in other markets like Australia for a few decades. They form the mainstay of retirement portfolios because of their relatively high yield.
There are some advantages compared to buying your own real estate/properties – firstly, REITs are pooling investors money so they can buy a portfolio of larger A grade commercial properties that can be leased out to blue chip tenants on long leases. You are unlikely to be able to buy such properties yourself and lease them to such tenants. secondly, the hassle of managing the property, collecting rent etc is all taken care of.
The disadvantage could be that the price of the REIT unit could trade at a discount from time to time. I will explain this in a video in the Fast Finance series soon. You might want to watch the series so you understand some basic terms and concepts. https://www.youtube.com/playlist?list=PL2Ao-D9S_7aC7UfLfu_Xtzrw0SoxCKqn3