If you hold DOT in AirGap, you can stake them to earn rewards. See the following guide for more info: https://medium.com/airgap-it/airgap-adds-polkadot-support-with-delegation-a4d14a8b55d3
There is currently a minimum amount of DOT required for each nomination. The threshold is currently around 250 DOT and is changing daily. Use this (unofficiall) website to see the current threshold: https://polkaview.network/dot If you delegate an amount below that threshold, you will not receive rewards!
|Locked while staking||Yes|
|Undelegating period||28 days|
|Rewards after||1 day|
|Slashing Risk||Yes (If Validator gets slashed, you lose a percentage of your funds)|
|Payout||Needs to be claimed by someone (Usually done by the Validator, so no claiming necessary)|