Regardless of whether the market is moving up, down, or sideways there is usually at least one opportunity available to execute an arbitrary order. While there is some risk involved in the real world application of using arbitrage, nobody should every assume that making money with investments is going to be easy or risk-free.
By analyzing the pricing differences, as well as the available buying and selling orders you can potentially make a purchase of bitcoin or an altcoin on one exchange, and then simply transfer it to another exchange where there are buying orders to purchase it from you at a higher price
You have to beware that prices are always subject to change on anything at a moment’s notice, which can evaporate your potential earnings. This can leave you being the bag-holder for someone else’s winfall. You can also run into selling walls, so before you go attempting to move coins to a market with a high asking price be sure to find out if there are actually orders being filled at those prices.