# Applying Artificial Intelligence in Cryptocurrency Markets: A Survey
## 2 Cryptocurrency Markets
### A Short Background on Cryptocurrencies
At a technical level, altcoins use almost the same or similar blockchain technology used by Bitcoin. Nevertheless, altcoins fundamentally seek to introduce some new alternative features compared to Bitcoin to increase their market share. For instance, Ethereum incorporates almost all of Bitcoin's attributes with additional features such as a fee limit or a digital platform to run smart contracts (SC) [26]. Litecoin, as another example, is designed to cope with the computational requirements for mining cryptocurrency coins. Furthermore, the aim of creating Dash coin is to have a faster transactions process and \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Attributes** & **Money** & **Electronic** & **Virtual** \\ \hline Money format & Digital & Digital \\ \hline \multirow{2}{*}{Acceptance} & By undertakings other than the issuer & Usually within a specific virtual community \\ \hline Legal status & Regulated & Unregulated \\ \hline \multirow{2}{*}{Issuer} & Legally established electronic money institution & Non-financial private company \\ \hline \multirow{2}{*}{Supply of money} & Fixed & Not fixed (depends on issuer’s decisions) \\ \hline Supervision & Yes & No \\ \hline Type of risk & Mainly operational & Legal, credit, liquidity, and operational \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of electronic money and virtual currency based on the definition of the European Central Bank. extend privacy protection [27]. Aside from the technical differences, cryptocurrencies can generally be categorised as follows. * Mining-based altcoins: they have similar characteristics to Bitcoin, and as the name implies, they use the typical mining process for generating new coins. One of the most famous leading altcoins belonging to this category is Ethereum. * Stablecoins: One of the main issues of mining-based cryptocurrencies is high volatility and fluctuation in their prices, making their trading complicated. Hence, stablecoins were introduced to address this challenge, which is valued based on stable existing currencies such as fiat currencies. Additionally, stable assets behind stablecoins secure and support their value. For example, Diem (previously Libra), developed by Facebook, and Tether, with the highest capital among stablecoins, are two famous coins in this cryptocurrency category. * Utility tokens: this type of cryptocurrency can give value to its investors by providing access to a future product or service. For example, Filecoin is a famous open-source cryptocurrency that aims to store data on hard drive storage spaces compared to cloud storage companies such as Amazon. Cryptocurrencies can also be categorised based on the currency domain, platform category facilities, and the domain of application [28]. The cryptocurrency ecosystem mainly relies on many exchanges as they provide trading tools for investors. Exchanges facilitate cryptocurrency trades and allow traders to sell or buy digital assets for other assets, primarily fiat currencies. Centralised exchanges (CEX), decentralised exchanges (DEX), and hybrid exchanges are three types of cryptocurrency exchanges. CEX is governed by a corporation, such as Binance and Coinbase. DEX provides an automated process for peer-to-peer trades. For example, DODO and Uniswap are part of this group. Finally, hybrid exchanges, as the name implies, are a combination of both centralised and decentralised exchanges [29]. There are numerous cryptocurrency exchanges worldwide. For example, Bitcoin can be traded in various currency cross pairs in at least 387 markets [30]. Payment methods, supported coins, transaction fees, transaction speed, and trading volume are a few factors of an exchange's popularity. Table 3 presents a number of the most known exchanges along with their specifications. The number of supported coins in the second column of the table shows the number of cryptocurrencies available in the exchanges for trade.