What were trade unions and what did they seek to accomplish?

Trade Unions were, and are, groups for working people.

They aim to get a better deal for their members (and by extension all workers in their field) by using collective bargaining, withholding labour, or other tactics. By all standing together and making demands it prevented the owners of factories or mines or mills just firing the "troublemakers". Unions work(ed) best in the skilled trades sectors, where good workers were hard to replace.

They began during the industrial revolution and helped the often uneducated, poor and disenfranchised workers to stand up to their bosses, obtaining better pay, holiday entitlements, safety improvements etc.

There is an uneasy balance to be struck between profit for a company and it's payment and treatment of it's workers. Unions exist to uphold the worker's end of this balance.