Trade Union Act was established in the year 1926. TU is any association (temporary /permanent) for the purpose of regulating the relationship between employers-workers, employer-employer, worker-worker for imposing restrictive conditions on trade practices. It also includes federation of unions referred as association of professional persons. In countries like England, trade union is referred as association of professional person. In India it is considered as cursi - union /semi- union. In America, TU is considered as the association of all persons in a trade.

Functions of TU: functions can be categorized into:

1. Militant /protective

2. Positive/fraternal.

3. Intramural/extramural 

1. Militant /protective: as the name suggests it protects their members, aims at securing better conditions of work, employment for members. It uses instruments like strikes, lockouts etc. for protecting the interest of their members. 
2. Positive/fraternal: It provides financial support to their members during time of temporary unemployment. 
3. Intramural/extramural: intramural refers to welfare schemes & activities within the framework of factory premises (safety, secure working environment, minimum wages, minimum working hours, and leave with wages) Extramural refers to the welfare schemes outside the factory premises (medical assistance, health care, education etc.) 

TU are born out of the necessities of the workers to protect and defend them from injustice, encroachment and wrong. Unions classified according to purpose: Under this head, normally two types of unions have been kept

1) Reformist

2) Revolutionary

1. Reformist Unions: These unions are those which aim at the preservation of the capitalist society and maintenance of the usual employer-employee relationship, elimination of competitive system of production. The reformist unions have been subdivided by hoxie according to the objectives: into business unions and uplift unionism. 
2. Revolutionary Unions: These unions aim at destroying the present structure completely and replacing it with new and different institution according to the ideas that are regarded as preferable. The revolutionary unionism is also of two types namely, anarchist and political. Dr horie also enumerates a third type of unionism namely predatory unions and gorilla union.

According to membership structure there are four types of Trade unions:

1.Craft unionism 

2. staff unionism,

3. Industrial union and

4.general union.

1. Craft Union: Workers, those are working in same as similar type of work/trade/business. They have similar skills, specialization. Members are mostly non manual workers. Members are craft conscious than class conscious .They take the membership on the basis of similar type of work. They strengthen their union by integration of their members. 
2. Staff Union: Organization, those are basing upon a sense of common status, same type of need. They try to seek their membership from non manual sectors of the economy like clerical, supervisors, operators, technicians, craftsmen etc. Unique feature of staff union was women workers were also members of staff union. Staff union gained popularity by taking women workers as their members.
3. Industrial Union: Irrespective of crafts, skill, grade, position, gender etc. The workers working in one industry were members of industrial union. This union is more class conscious than trade conscious. 
4. General union: It covers all types of industries. Labor class people from any type of industry can be members of general union. It is more open than the industrial unions. Their numerical strength is high.