One of Yearn's most popular products are the yVaults.
The goal of the Vaults program is to empower the community to quickly and safely create and utilize the most effective yield farming robots created by the industry's best strategists.
yVaults have charge fees on deposited assets and the generated yield, see the FAQ for more details. Profits generated are used to purchase more of the underlying asset of each vault (e.g., the YFI vault's profits are used to purchase additional YFI); therefore, the vaults represent a continuous buy-and-hold strategy. Withdrawals are allocated on a pro-rata basis determined by the share each depositor contributes to the pool.
Currently there are 2 versions of the yVaults available in our yearn.finance website. You can see from the list which vaults are V1 and which are V2. Tokens are deposited into their respective yVaults and are then reinvested based on the best current opportunities in the market.
For the end user the main difference is the fees charged, the relevant section in the FAQ has more details. Once you understand it, pick the yVault that matches your tokens and the APY desired.