The existential deposit (ED) refers to the minimum amount of cryptocurrency required to keep an address or account active on Polkadot and most Substrate chains.
For DOT, the existential deposit is 1 DOT. This value differs for the different chains within the Polkadot ecosystem, and is often denominated in the chain's native token.
If your account falls below this value, your account will be reaped. This will render the account inactive, and the remaining funds will be burned. However, you may reactivate the account again by sending more funds to the original address.
On the Extension
Talisman extension wallet prevents account reaping by warning users when they are about to engage in an asset transfer that results in the balance being lower than the existential deposit. Users may proceed with the transfer at their own discretion.
On the Portal
The Talisman Portal also prevents the user from actions that would result in the account balance being lower than the existential deposit.
This is most commonly encountered during staking. For example:
You may have 1.0001 in DOT, and want to claim your stake
However, the fees required to execute the transaction may be around 0.005 DOT
If the transaction were allowed, that would put you below the existential deposit
And so, in these cases, the stake/re-stake action would be blocked by the Portal
In summary, please always remember that there are transfer fees involved in any transfer or transaction, and be sure to keep enough tokens in your account to cover these fees.