Karma Yoga is a Yogic lifestyle, also called “the path of selfless work,” “the path of selfless service,” or “the path of unselfish action.” It’s considered one of the four classical Yoga paths besides Jnana Yoga (Path of Knowledge), Raja Yoga (Path of Meditation) and Bhakti Yoga (Path of Devotion).
The idea behind doing this type of Yoga is to “get rid of the Ego” by only doing activities that serve others — with your efforts given to “right causes” — where “others” are essentially seen as individual expressions of God or the Divine.
Doing Karma Yoga also implies that one does work without expecting any reward, praise, or result for/of the services one has performed. In fact, it’s a form of practicing complete worldly detachment, which is seen as a means to achieve spiritual liberation.
Other elements associated with doing Karma Yoga are universal compassion, accumulating merit or eliminating bad Karma, loving kindness, and worship of and union with God (or the Divine).