The blockchain fee, also called the 'miners' fee is a bitcoin transaction fee that is charged to users when performing bitcoin transactions. The fee is collected to reward miners for maintaining the Bitcoin network.
You need to pay the blockchain fee to ensure your bitcoin transfers arrive in a timely manner. The blockchain fee is one of the main tools used to speed up bitcoin transactions, which are often slow due to high congestion on the Bitcoin network. The lower the blockchain fee, the lower your transaction's priority in the Bitcoin network.
You can find more information about blockchain fee in this Bitcoin Wiki article.
Note: The blockchain fee is not a Wirex fee. It is a standard fee that is applied to all on-chain bitcoin transactions.
Related article: My blockchain fee is too high. Why? What should I do?