Nations that print currency have two strategies for using their currency to maximize their economy. I'm going to call them Strong Currency Strategy and Weak Currency Strategy.
In Strong Currency Strategy, effort is applied to keep the value of the currency high. This makes your currency an excellent hedge choice for investors fearful of falling value, and your citizens love it because foreign goods are now, to them, super cheap. It works best for postmodern economies with lots of services. Germany is famous for using this strategy.
In Weak Currency Strategy, the currency is deliberately allowed to inflate until it trades very poorly. Traveling people with weak currencies are unhappy at the exchange rate, but it serves to make your country attractive to industry. After all, if a company can pay all expenses in weak currency, but be paid in strong currency, they make out like bandits, and the foreign spending replenishes the lost value. The constant printing of money lowers the tax burden, further pleasing manufacturers. Traditionally, France, Spain, and Italy have opted for this strategy.
There are other strategies like North Korea's autarkic "Juche," but I'll leave discussions of those to professional economists.
So, let us imagine a world with two countries, and two currencies. I'll call the currencies the "Deutschemark" and "Lira" after Germany and Italy's traditional currencies. Let us say that the "Deutschemark's" issuer is perusing strong currency strategy and the "Lira's" issuer is pursuing weak currency strategy. Each country has certain industries, both have a strong tourism industry that appeals to each other, and industries that work more strongly in one than the other. Probably the Deutschemark's issuer will have more banking, and the Lira's issuer will have more farming.
Deutschemark holders will love buying food from the other country, since even 1 mark will buy them a huge amount of food. Likewise, Lira-holding farmers will love borrowing money from the other country, because they can do a lot on relatively little. Lira-land also gets a huge boost from Deutschemark-land's tourists. There's also huge incentives to borrow money from Deutschemark-land's banks and run factories in Lira-land. Everybody wins. Well, not everybody. Lira-land tourists will find visiting the other country to be a massively expensive proposition. And running a factory in Deutschemark-land is a losing proposition too.
My country, the United States, has been pursuing a strong currency strategy for most of its existence. Traditionally it was backed by gold for strength, but that's been done away with in favor of controlled inflation instead. There are many who'd like to switch to weak currency strategy, but I think that's a bad idea.