"Staking" your GHST does not allow anyone else to access, withdraw, change or use your GHST tokens. You can stake or unstake at any time. Staking simply lets Aavegotchi know that you have tokens so that you can be rewarded with FRENS. FRENS are not ERC-20 tokens and are not tradeable, but your balance accrues in real time after staking and can be seen on the Stake GHST and Tickets pages.
What are FRENS?
FRENS can be converted to six different rarities of wearable raffle tickets; and, also, to drop tickets which can be entered in land raffles and portal raffles. These raffles will always be announced ahead of time. You can see the stats from the last wearable raffle here and land auction here.
Simply put, staking GHST allows you access to a broad array of the future NFTs and/or the ability to sell raffle tickets for GHST to compound your GHST stack or to another token to take profit from the generous APY.