Fiat currency: This refers to a government-issued currency that is not backed by a physical commodity, such as gold or silver. Instead, fiat currencies are backed by the trust in the government that issued it. Examples: USD, JPY, etc.
Cryptocurrency: It is a digital form of currency that uses cryptography and blockchain technology to provide a safer, faster and better form of money, more adapted to a digital world. e.g.: Bitcoin (BTC), Ethereum (ETH), Litecoin(LTC) Cardano (ADA), etc.
Stablecoin: It is a class of cryptocurrency that attempts to combine the technological benefits of cryptocurrency but with reduced price volatility. These types of currencies are backed by a reserve asset (collateral), e.g.: USDT (USD), USDC (USD), DAI (Ethereum), etc.
Crypto wallet: It is a digital wallet that allows users to store and manage their cryptocurrencies. It can either be Software that you install on your laptop or smartphone (SW Wallets), or it can be physical devices (HW Wallets). A wallet has both public and private keys. e.g.: SW Wallets (Exodus, Trust wallet); HW Wallets (Trezor, Ledger).
Public key: This is the public address associated with the wallet, like a bank account number. In crypto transactions, it is the public key that is used to identify the receiver of the transaction. That means that you must share your key with someone before they can send you crypto.
Private key: It is the security key, like a pincode, that is used to authorise (sign) transactions from your wallet into other wallets. NEVER share your private key.
Transactions: These are messages, like email, which need to be digitally signed using a private key. Transactions enable you to send currency from one wallet to another through the currency network.
Blockchain: This is a digital ledger were all the transactions made on the network are recorded.
Crypto exchange: This is a place where you can buy and sell crypto. E.g.: Coinbase, Kraken, Binance, etc.