Karma refers to intentional actions that lead to future consequences. The Bhagavad Gita refines this into three types: Karma, Akarma, and Vikarma.
Krishna explains in Chapter 2, Verse 47 that you have a right to the action only, never to its fruits.
It means focusing 100% on the quality of your work today, rather than worrying about the promotion or praise tomorrow.
A psychological state of 'Flow', where you are so absorbed in the process that the outcome doesn't distract you.
An artist painting for the love of the art, not just to sell the canvas for a high price.