Crowdsale is the central concept used in ICOs. Crowdsale is the process, when a quantity of a certain cryptocurrency is sold in the form of tokens. These tokens are promoted as future functional units of currency if or when the project launches. As an example, the development of Ethereum was funded through an online crowdsale in which 11.9 million coins (ETH) were distributed prior to the launch of the network.
Trezor users interested in emerging cryptcurrencies and crowdsales should be careful, as crowdsales are risky and largely unregulated.