What are Initial Coin Offerings (ICOs)?

As a seasoned professional in the realm of cryptocurrency and finance, I'm curious to delve deeper into the nuances of Initial Coin Offerings, or ICOs. Could you elaborate on the definition and workings of this phenomenon? Specifically, I'm interested in understanding the role ICOs play in funding blockchain-based projects, the risks and rewards involved for investors, as well as the regulatory landscape surrounding these offerings. Your insights into this fascinating yet complex topic would be greatly appreciated.