What is the difference between buying and selling cryptocurrencies?

Excuse me, could you please elaborate on the distinction between purchasing and selling cryptocurrencies? I'm curious to understand the key differences in these two transactions, as they seem to be fundamental concepts in the realm of cryptocurrency trading. Is it simply a matter of exchanging fiat currency for digital tokens versus the reverse? Or are there more nuanced factors at play, such as market conditions, transaction fees, and potential gains or losses? I'm eager to gain a deeper understanding of the intricacies involved in buying and selling cryptocurrencies.