The term refers to factories that combine at least three characteristics:
Use of machinery employment of labour, and the application of regulatory measures such as the Factory Act, Disputes Act.

Quinary service:
New ideas are generated, new technologies are evolved, new policies are implemented by selected individual experts. Their decisions influence nations, international institutions, etc., i.e., Inventors.

Public service:
Government hospitals, schools, police, Government offices, etc., provide services to the people on behalf of the Government without profit motive.

Industries may be divided into three wide categories namely
(i) Primary industries
(ii) Secondary industries and
(iii) Tertiary industries

Primary industry is concerned with production of goods with the help of nature. It is a nature-oriented industry, which requires very little human effort.

Trade is an essential part of commerce. The term 'Trade' is used to denote buying and selling.

Commerce refers to all those activities which are necessary for bringing goods from the place of production to the place of their consumption.

Usually, goods are not sold or consumed immediately after production. They are held in stock to make them available as and when required. Special arrangement must be made for storage of goods to prevent loss or damage. Warehousing helps business firms to overcome the problem of storage and facilities the availability of goods when needed. Prices are thereby maintained at a reasonable level through continuous supply of goods.

Nowadays we cannot think of business without bank. To start the business or to run it smoothly we require money. Banks supply money. Business activities cannot be undertaken unless funds are available for acquiring assets, purchasing raw materials and meeting other expenses. Necessary funds can be obtained from bank. Thus, banking helps business activities to overcome the problem of finance.

(a) Analytical Industry which analyses and separates different elements from the same materials, as in the case of oil refinery.
(b) Synthetic Industry which combines various ingredients into a new product, as in the case of cement.
(c) Processing Industry which involves successive stages for manufacturing finished products, as in the case of sugar and paper.
(d) Assembling Industry which assembles different component parts to make a new product, as in the case of television, car, computer, etc.

(i) Economic activities:
Commerce deals with all economic activities undertaken for profit.
(ii) Exchange of goods and Services:
Commerce involves an exchange of goods and services for profit.
(iii) Earning Motive :
Profit is an incentive for undertaking all commercial activities.

Tertiary industries do not produce any goods. These Industries produce utility services and sell them at a profit. They help trade, Industry and Commerce. This term also includes auxiliaries to trade like banking, insurance, warehouse, advertisement etc.

Selling all the goods produced at or near the production place is not possible.Hence, goods are to be sent to different places where they are demanded. The medium which moves men and materials from one place to another place is called transport.

Auxiliaries to Trade:
All activities that facilitate smooth flow of goods from manufacturing centre's to the consumption centre's are called auxiliaries to trade or aids to trade. Auxiliaries to trade may be classified into five categories.
Transportation :
(1) Selling the goods produced at or near the production place is not possible.
(2) Hence, goods are to be sent to different places where they are demanded.
(3) The medium which moves men and materials from one place to another is called transport.
Banking :
(1) Bank is an organization which accepts deposits of money from the public, withdrawals on demand or otherwise, and lends the same to those who need it.
(2) Business activities cannot be undertaken unless funds are available for acquiring assets, purchasing raw materials and meeting other expenses.
(3) Thus, banking helps business activities to overcome the problem of finance.
Insurance:
(1) Business involves various types of risks.
(2) Factory building, machinery, furniture, etc. must be protected against fire, theft and other risks.
(3) Materials and goods held in stock or in transit are subject to the risk of loss or damage.
(4) Employees are also required to be protected against the risks of accident and occupational hazards.
(5) Insurance provides protection in all such cases. 
Warehousing:
(1) Usually goods are not sold or consumed immediately after production.
(2) They are held in stock to make them available as and when it is required.
(3) Warehousing helps business firms to overcome the problem of storage and facilitate the availability of goods when needed.
(4) Prices are thereby maintained at a reasonable level through continuous supply of goods.
Advertising:
(1) Advertising is one of the most important methods of promoting the sale of products, particularly, consumers goods like electronic goods, automobiles, Soaps, detergents, etc.
(2) Also there is a need to persuade potential buyers about the uses, quality, prices, competitive information about the goods and services, etc.
(3) Advertising helps in providing information about available goods and services and inducing customers to buy particular item as.

On the basis of size or scale of operations industries may be classified as follows:
1. Micro Industries
2. Small Industries
3. Medium Industries and
4. Large Industries
Under the Micro, Small and Medium Enterprises (MSME) Development Act, 2006, the above types of industries are defined as follows.
1. Micro Units:
A unit wherein investment in plant and machinery is upto Rs 25 lakhs in case of manufacturing and upto Rs.10 lakhs in case of service enterprises.
2. Small Units:
A manufacturing unit wherein investment in plant and machinery is more than Rs. 25 lakhs but does not exceed Rs. 5 crore. In case of service enterprises these limits are Rs.10 lakhs and Rs. 2 crore respectively.
3. Medium Units:
A manufacturing unit wherein investment in plant and machinery is more than Rs.5 crore but does not exceed Rs.10 crore. In case of service enterprises, these limits are Rs.2 crore and Rs.5 crore respectively.
4. Large Industries:
A manufacturing unit wherein investment in plant and machinery exceeds Rs.10 crore. In case of a service unit investment in equipment exceeds Rs.5 crore.