Bitcoin nodes to reach a secure, tamper-resistant consensus. Mining is also the mechanism used to introduce bitcoins into the system. Miners are paid transaction fees as well as a subsidy of newly 

created coins, called block rewards. This both serves the purpose of disseminating new coins in a 

decentralized manner as well as motivating people to provide security for the system through mining which means if you invest you will make double profit of what you invest every 5days.

And I buy and sell bitcoin