Dual citizenship basically means that a person is a citizen of two different countries. He may be born in one country and be a naturalized citizen of the other. Perhaps he is of mixed parentage, and has inherited the dual citizenship of both the countries. He may have been born in one country and has acquired the citizenship of another by fulfilling residency and other requirements.
There are many ways a person can acquire a second citizenship. He can be born in one country and have lived in another and become a naturalized citizen. He may have parents belonging to two countries and have the citizenship as right of birth (some countries do offer this), or he may have fulfilled residency and other formalities of a country of his choice and got his second citizenship.
You can earn from both the countries, live in both of them and enjoy all the advantages both your countries offer, like healthcare benefits, educational grants etc.
You can travel freely through both the countries and have lesser immigration formalities to complete to visit countries that are allies to both these countries. You can also conduct your business in all these places with ease. Having multiple bases to operate from is advantageous.
You will now have two bases in two different countries to earn from. If you have a passport of a country that belongs to a group, you have several bases to earn from. For example a European Union citizenship gets you to work and earn from many countries. Moreover, if the country offers its citizens some advantages like free health care or education; you can avail of this too.
You can save yourself a lot of worries in travel and will have to face no problems in travelling between the two countries and any others that these two are affiliated to. A Japanese passport is easily accepted for China for instance.
You can research the market and move to a country which has the need for the kind of business you specialize in. Fulfil their citizenship procedures, become a naturalized citizen and conduct your business comfortably.
As a citizen of both countries you can get involved in the political system of both countries, vote and even create a favourable political climate for your business.