Cryptocurrency can be easily understood as a digital money that can run on its own over the Internet via peer-to-peer. The most important aspect of Cryptocurrency is the blockchain. Think of it as a public record of everything that is going on and can easily be seen by the public. Think of a Cryptocurrency as our agreed upon digital money where all transactions that we do get recorded in a ledger and all of us agreed that what’s written in the ledger is valid. In Cryptocurrency, the money or asset reside in a code that everyone agreed on. All transactions are recorded and are agreed upon by every users well without you needing to do anything (it’s not like you have to manually approve all transactions).
Ideally, Cryptocurrency should be decentralized. This means no single entity controls your coins or the entire community. You can do whatever you want with your cryptocurrency, unlike in some digital currencies (mobile credits, electronic money services by some telcos or even game creators), your balance resides in their system and you can’t use it on anything else that is not part of their system and if they close out then your credits will be unusable.
These are softwares that you can use to act as storage of your cryptocurrency. It can be a mobile wallet, a desktop wallet (windows, linux, mac) or online wallet where you only need your browser and an Internet connection to access.
These are the 3rd party websites (or even in-house) that operate as online cryptocurrency exchange. These exchanges have dozens of cryptocurrencies, which you can exchange with one or the others ,so if you want to buy/sell your cryptocurrency, this is the place to go to.