Question

what are MNCs describe their functions

Answer 1

Multi national cooperations are called MNCs
their main function is to make foreign direct investment .
they also play a vital role in economic development of a country.

Answer 2

A multinational corporation or multinational enterprise is an organization that owns or controls production of goods or services in one or more countries other than their home country. 

The distinctive features of multinational companies are as follows.

1. Large Size:
A multinational company is generally big in size. Some of the multinational companies own and control assets worth billions of dollars. Their annual sales turnover is more than the gross national product of many small countries.
2. Worldwide operations:
A multinational corporation carries on business in more than one country. Multinational corporations such as Coco cola has branches in as many as seventy countries around the world.
3. International management:
The management of multinational companies are international in character. It operates on the basis of best possible alternative available any where in the world. Its local subsidiaries are managed generally by the nationals of the host country. For example the management of Hindustan Lever lies with Indians. The parent company Unilever is in The United States of America.
4. Mobility of resources:
The operation of multinational company involves the mobility of capital, technology, entrepreneurship and other factors of production across the territories.
5. Integrated activities:
A multinational company is usually a complete organisation comprising manufacturing, marketing, research and development and other facilities.
6. Several forms:
A multinational company may operate in host countries in several ways i.e., branches, subsidiaries, franchise, joint ventures. Turn key projects.

Now your question asks "What they do ?"

Multinational companies make investments in different countries with the following aims.
(a) To take tax benefits in host countries;
(b) To exploit the natural resources of the host country;
(c) To take advantage of Government concessions in host country;
(d) To mitigate the impact of regulations in the home country;
(e) To reduce cost of production by making use of cheap labor and low transportation expenses in the host country.
(f) To gain dominance in foreign markets;
(g) To expand activities vertically.