A term used for when ICOs will put up their tokens for sale.
The date of launch is just one part of any ICO campaign: it is a point at which the sale of the asset to the general public begins. It is usually preceded by several months of intense preparation and, sometimes, one or more private sale rounds that distribute a smaller amount of the asset among a group of select investors.
Prior to starting the sale, the development team needs to design at least the basic technology behind their cryptoasset, ensure necessary legal compliance, develop a distribution plan and write and publish all the relevant documentation and much more.
This is why the date of launch is usually known to the public well in advance: to give the developers the opportunity to work with the community feedback and to provide time for a comprehensive marketing campaign to hype up the ICO.