Cryptocurrencies are innovative digital currencies that use cryptographic techniques to secure transactions. They have become ubiquitous in the modern financial world and have a variety of applications, including buying, sending money and investing. Wallets, which can be online, mobile, hardware or paper, are used to securely store and manage cryptocurrencies. The key technology that makes cryptocurrencies work is the blockchain. Blockchains represent a distributed public registry of all cryptocurrency transactions, ensuring their transparency and integrity. Bitcoin, as the first and most famous cryptocurrency, enables faster, secure and cheap transactions around the world. Ethereum, on the other hand, stands out for its ability to execute smart contracts, which opens the door for various applications in decentralized applications. An essential characteristic of cryptocurrencies is decentralization, meaning that there is no central authority that controls the cryptocurrency or transactions. This provides users with greater autonomy, but at the same time brings challenges in regulation and acceptance by traditional financial institutions. Smart contracts enable the automatic execution of transactions and agreements, which opens possibilities for automating business processes and eliminating intermediaries. In the world of cryptocurrencies there are also some challenges and phenomena that need to be taken into account. Crypto manipulation is a negative phenomenon in which the values of cryptocurrencies are deliberately manipulated for financial gain. Meme coins are cryptocurrencies based on entertainment content, and the play-to-earn concept allows users to earn cryptocurrencies by participating in games.