How did labor unions improve the working conditions for American workers?

Read Samuel Gompers testimony before Congress regarding the AFL and the original platform of the Knights of Labor from the links below. What issues did labor unions attempt to resolve in the early 1900s? How successful were they at resolving these issues? Why was there such a struggle between business and labor, why was it so difficult for them to come together. Why were strikes so violent? (Not being recognized, the issues they were trying to resolve, etc.) How did labor unions improve the working conditions for American workers?

http://www.digitalhistory.uh.edu/teachers/historyonline/gompers_amfedlabor.cfm

https://lopes.idm.oclc.org/login?url=http://search.credoreference.com/content/entry/abcamlabor/appendix_27_knights_of_labor_preamble_and_platform_to_their_constitution_1891/0

Just need 125 words