An ICO (Initial Coin Offering) is an initial token offering, a way of raising funds to launch a crypto project. In essence it is an analog of a public share offering, but in the world of blockchain.
An advisor is a consultant for a crypto project, most often an experienced specialist in the field of blockchain, technology or finance, who advises the team and increases trust in the project.
A crowdsale is the public sale of tokens of a new crypto project, during which the team raises funding while participants acquire tokens before they reach the open market, often on more favorable terms.