The successor organization of the General Agreement on Tariffs and Trade (GATT) is the World Trade Organization (WTO).

Explanation:

1. General Agreement on Tariffs and Trade (GATT):
- GATT was established in 1947 as an international trade agreement.
- It aimed to promote international trade by reducing trade barriers such as tariffs and quotas.
- GATT provided a framework for negotiating trade agreements and resolving trade disputes among its member countries.
- However, GATT lacked a formal institutional structure and enforcement mechanism.

2. Creation of the World Trade Organization (WTO):
- In 1995, the World Trade Organization (WTO) was established as the successor organization of GATT.
- The creation of the WTO was the result of the Uruguay Round of negotiations, which lasted from 1986 to 1994.
- The WTO's establishment aimed to strengthen and expand the rules-based international trading system.

3. Functions and Objectives of the WTO:
- The WTO serves as a forum for member countries to negotiate and set rules for international trade.
- It provides a platform for resolving trade disputes through its Dispute Settlement Mechanism.
- The WTO promotes and facilitates the liberalization of trade through negotiations on various trade issues, including agriculture, services, intellectual property, and investment.
- It administers trade agreements and monitors the trade policies of member countries.
- The WTO also provides technical assistance and capacity-building support to developing countries to help them participate effectively in the global trading system.

4. Key Principles of the WTO:
- Non-Discrimination: The most-favored-nation (MFN) principle ensures that countries do not discriminate between their trading partners.
- Reciprocity: Countries are expected to provide trade concessions in exchange for concessions from other countries.
- Transparency: The WTO encourages its members to provide information about their trade policies and regulations.
- Predictability: The WTO aims to create a stable and predictable trading environment by reducing trade barriers and limiting the use of trade restrictions.

In conclusion, the World Trade Organization (WTO) succeeded the General Agreement on Tariffs and Trade (GATT) in 1995. The WTO plays a crucial role in facilitating international trade, resolving trade disputes, and promoting the liberalization of global trade.