For every transaction with cryptocurrencies a fee (also known as mining fee) is required.
These transaction fees are paid to the servers to confirm the transaction.
It depends on the cryptocurrency if this is a fixed rate or a percentage.
It is really important to send these fees. If you do not send these fees you have the risk of failed transactions.
Most wallet programs already calculate the required transaction fees. Some programs even have a slider to decide how much transaction fees will be sent to make the confirmation of the transaction faster.