Introduction To Finance

1) Why do countries have currencies with different values to each other?

The relationship of one country's currency to another is different, based on the country's economy and political stability.  Those factors are changing constantly. If a country has a strong economy, the money it makes is worth more in relation to the currency of a country with a weak economy.
The value of a country's currency also depends on political stability. Now, instead of gold or silver, "confidence" backs the world's currencies. The only reason that anyone is willing to accept paper money in exchange for their goods or services is because they're confident that they'll be able, in turn, to pass the paper money on to someone else in exchange for the things that they want or need. If you think, you can't exchange your money anymore, you will less likely buy this currency. As a result its value goes down.

2) How does a nation gain and / or lose when the value of their currency fluctuates?

If a country's currency's value is low in comparison to other currencies, it can export more because other country's currency's buying power is higher (their value is higher). On the other hand the country with the low currency can import less because it can buy less in other countries.
When a currency's value goes up on the Forex market, investors are more likely to buy this currency meaning a boost of this country's economy. Speculators also play a role in influencing a nations gain or lose of money : if they massively buy a currency its value goes up resulting in bigger buying power for this nation and vice versa if speculators sell huge amounts of currency its value goes down resulting in less buying power.

3) How can government actions (central banks) affect the value of their currency and why do they do so?

If a central bank prints more money and when the prime lending rate is low, that means that banks are lending more money from the
central bank and consequently can give out more bank loans. More money is in circulation and the value of this currency declines (monetary inflation). On the other hand, if a central bank prints less money and the prime lending rate is high the result is deflation.

4) How does a currency trader make and lose money?
A currency trader tries to buy a currency of whom he knows that its value will increase compared to the currency he exchanged it for.
When its value goes up (as expected) the trader can resell it and gets more money out of it than he invested.

Business proposal
I wish to set up an online e-commerce platform selling wine from France. The business will buy wine in France directly from the producers or a distributor and sell it online. The e-platform includes a possibilty for online payment and international shipping. The customers will be businesses like restaurants or hotels as well as individuals.  Starting costs will be funded with a bank loan : the money will be invested in developping the e-platform, buying an conveniant place to store the wine and to buy the wine itself. In the beginning advertising will be exclusively online by Google adwords, social networking (twitter) and SEO. There will be 2 employees (salary depending on sales).