Vesting refers to the gradual 'unlocking' and transfer of assets from a party that has raised funds to a party that has invested funds.
Vesting can take place using 'traditional' off-chain financial infrastructure or on-chain using smart contracts. Examples of token vesting include transferring company shares to seed investors or cryptoassets to ICO investors.
Different cohorts of investors may be subject to different vesting periods, nominal allocations, prices, and levels of assurances, such as legal conditions/limitations or on-chain logic. These factors may affect the supply/demand dynamics in secondary markets.