I am having hard time understanding these concepts:

pooling, trust (how are these different?)
holding companies
interlocking directorates
vertical and horizontal integration

can anyone help me?

Try lookig each up at:
http://en.wikipedia.org/wiki/Main_Page

Use the search box on left when you get there.

Of course, I can help you understand these concepts. Let's start with each concept one by one:

1) Pooling and Trust: Pooling refers to the practice of combining resources or assets from multiple entities or individuals into a single entity. This can be seen in the context of pooling funds or resources together for a specific purpose, such as a group of individuals pooling money to invest in a project. On the other hand, trust refers to a legal arrangement where one party, known as the trustor, grants another party, called the trustee, the authority to hold and manage assets on behalf of a third party, known as the beneficiary. In simple terms, pooling is the act of combining resources, while trust is a legal structure for managing and protecting assets.

2) Holding Companies: A holding company is a type of company that does not have any operational activities of its own but instead owns and controls other companies. It holds the majority of shares or controls the board of directors of its subsidiary companies, also known as operating companies. The main purpose of a holding company is generally to manage and control these subsidiaries, strategically invest in different businesses, and facilitate consolidation or diversification of assets.

3) Interlocking Directorates: Interlocking directorates refer to a situation where one or more individuals serve as directors on the board of multiple companies. This can occur when a person serves on the board of directors of one company and simultaneously serves on the board of directors of another company. Interlocking directorates often arise when two or more companies have overlapping ownership or business relationships.

4) Vertical and Horizontal Integration: Vertical integration refers to the strategy by which a company expands its business operations by acquiring or merging with companies at different stages of the supply chain or distribution channel. For example, a car manufacturer acquiring a tire company or a retail company acquiring a distribution company. Horizontal integration, on the other hand, refers to a strategy where a company merges or acquires other companies operating in the same industry or at the same stage of the supply chain. This can lead to the consolidation of market share or the elimination of competition.

To further enhance your understanding of these concepts, you can visit the provided link, http://en.wikipedia.org/wiki/Main_Page, and use the search box on the left side of the page to search for each concept individually. Wikipedia provides detailed articles and explanations on various topics, which can help clarify any specific questions or doubts you might have.