Paris Convention
The Paris Convention applies to patents, trademarks, industrial designs, utility models, service marks, trade names, geographical indications, the repression of unfair competition and was signed in Paris, France on March 20, 1883. In essence, it ensures that each member nation tax citizens of the other member nations against unfair 
competition.
The Paris Convention centers around the notion of “national treatment,” which means that member nation must provide as much trademark protection to citizens of other member nations as it would to its own citizens.
The Paris Convention does not regulate the filing and registration of marks and leaves that to each member nation as governed by their domestic law. But, a member of the Paris convention can register its Mark and any other member nation by either (1) satisfying all the registration requirements that the nation imposes on domestic applicants; or 2) registering its mark in its home country and relying on that registration and its application to register abroad.
Trademark Law Treaty
The trademark treaty was negotiated with the help of the World Intellectual Property Organization. The aim of this treaty is to standardize and simplify the trademark registration process. Although the Trademark Law Treaty does not have a centralized registration system across multiple countries, the United States has ratified this Treaty.
The Madrid Protocol
The Madrid Protocol allows for trademark holders to file one application, in one office, in one language and ensures protection of the mark in multiple countries. United States joined the Madrid protocol in 2002. When the mark owner elects to file with the Madrid protocol he or she can designate how many other countries the owner wants to file their mark in. The mark owner pays a fee based on how many countries the mark is registered in. The filing is then forwarded to the International Bureau of the World Intellectual Property Organization.” the Bureau then takes care of the registration and publishes it in the WIPO Gazette of International Marks. Each country that the mark is registered in is then provided a copy from the Bureau.