It is the converting ordinary plain text into unintelligible text and vice-versa. It is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it.
The major concerns:
Cryptocurrency transactions are secured by cryptography. It is vital in sending coins and tokens between wallets without an intermediary like a bank.
The main solution cryptography provided was the ability to eliminate the double-spend without turning to a financial institution.