Airdrops and ICOs (Initial Coin Offerings) are both methods of distributing tokens, but they differ significantly:

Airdrop: Tokens are distributed for free, often to existing holders or as part of promotional campaigns. The goal is to raise awareness and build a community.
ICO: Investors purchase tokens before they are listed on exchanges, typically during the fundraising phase for a new project. ICOs offer early access in exchange for funding.
Airdrops are usually less risky for participants, while ICOs involve financial investment with the potential for higher returns or losses.