ICO is Initial Coin Offering from the word IPO (Initial Public Offering) so meaning is same overall. The start up company want to publish "The Coin" with the business plan for the long term.
The company build a projects and have developer, advisors and investor of course to starting the business. When "The Coin" released it has a initial value and will be launch in crypto market

For the example, Arcblock has a good prospect and I want to buy "The Coin" named ABT before launch so I can buy with lower rate and bonus offering from the company. When ICO release in market then the price will be going up.