An epoch is a distinctive period of time. In Pangaea every such epoch / period lasts for 10 minutes, which usually constitutes around 75 blocks.
The pre-staking phase of Pangaea will last for 144 epochs / 24 hours. After the pre-staking phase has finished the EPoS phase will start.
In EPoS a validator will go live within 1 epoch / 10 minutes of issuing the ./hmy staking create-validator command.
When you decide to undelegate your tokens from a validator in Pangaea your tokens will be subjected to a cooldown period lasting 7 epochs / 70 minutes.
This means that you won't have access to your tokens or can transfer them for 70 minutes after issuing the ./hmy staking undelegate command.