Transaction bitcoin charges usually occur for free if the amount of Bitcoin shipped exceeds 0.01 BTC. Bitcoin in small quantities is given to miners as a reward for processing the transaction and putting it into blockchain. For now, most transactions are processed for free, but for deals that attract coins from multiple Bitcoin addresses so that it requires a larger portion of data, it will incur very small transaction fees.
The fees displayed here are Satoshis (0.00000001 BTC) per byte of transaction data. Miners usually include transactions with the highest fee/byte first.
Wallets should base their fee calculations on this number, depending on how fast the user needs confirmations.