What is Gas Price and Gas Limit (ETH, ERC20)?

Gas Price and Gas Limit are Ethereum-only concepts.

Essentially they are very simple: the gas is used to power your transaction on the Ethereum blockchain. A standard Ethereum(ETH) transaction will generally use up to 21000 gas (with ERC20 tokens up to 100000 or even 150000). Token gas usage may vary. Essentially this means that you can pay no more than this gas amount per transaction. Gas price, on the other hand, is the amount of ETH you pay for each unit of gas. If set too low, no miners will mine your transaction and it will fail (My transaction fails with "Out of Gas" Error (ETH, ERC20)?).

Essentially transaction fees in Ethereum are defined as anything less than (Gas Price * Gas Limit).

Gas price is usually expressed in Gwei. 

1 Gwei = 0.000000001 ETH

So for example if you use a Gas Limit of 21000 and a Gas Price of 2.2 Gwei, that would mean 0.0000462 ETH.

But do not worry, since total Transaction Fee is calculated in EUR/USD/... Currency in BC Vault Application for your convenience.

With ERC20 tokens it might be you will actually pay less than what you see in transaction cost, as this will depend on actual gas used by the transaction. You will see the actual cost once transaction is successfully executed.

For latest info on Ethereum Gas prices go here: ETH Gas Station