We should have explained better and we will improve our website, sorry about that.

The blockchain that we are connected to is Bitcoin Cash(BCH). Bitcoin Cash is a fork of Bitcoin that aims at instant, cheap transactions. Bitcoin Cash transactions are instant unlike Bitcoin transactions. Each message costs around a cent as the fees is 1satoshi/byte(https://bitinfocharts.com/comparison/bitcoin%20cash-transact...).

The private key is being stored on the client side and we will open source the code soon so that users can verify that we do not store their private key. This is similar in functionality to Bitcoin wallets.