Karma Yoga or Yoga of Service, Path of work . Karma Yoga is the path of service for in this path, it is believed that your present situation is based on your past actions. So by doing selfless service now, you are choosing a future that is free from negativity and selfishness. Karma Yogis change their attitude towards the good and in the process, change their souls, which leads to a change in their destiny.
Lord Sree Krishna explained Karma yoga very detailed in the battle field of Kurukshetra
KARMA : The word originated from the root “KRU” meaning do, work, etc. Karma thus means action or work, and not the popular meaning of “fate”. There are two types of Karma- 1) Niskama Karma- work without attachment, which produces no bondage, and 2) Sakama Karma-all work done for some end result, which leads to bondage for the doer. The work may be to maintain your body, meet your official obligations, to upkeep your family, prayers & other religious activities, service to society or many other things. In Gita, the word Karma is used to denote all human activities.
YOGA: This word is used at innumerable places in the Gita with meanings like appropriateness, joining, expertise, attainment etc. The essential meaning of Yoga is explained by Sri Krishna himself as “Yogah Karmasu Kausalam” (Gita 2.50). Kausalam means a special talent, expertise or skill in doing something. So doing things with expertise is Yoga. A Yogi is one who does something with expert knowledge or skill.
So KARMA YOGA refers to all human activities performed with concentration, skill and finesse. The way to liberation is to perform your duties without attachment