Initial Coin Offering (ICO) is the most commonly used means of raising funds for blockchain-based projects.
It became especially popular because it used to be relatively easy to raise a substantial amount of money in a fairly short period of time. ICO investment was fabulously popular in late 2017 and towards the first three quarters of 2018 but their popularity has faded. This is because a lot of the projects turned out to be a scam, while the vast majority of them lost more than 90% of their value.