a person leaves a legacy that will be remembered for a long time, either good or bad.
Wikipedia:
"Legacies are, more or less, what we remember about a person or a country. What an individual or a country does today might, in the future, be regarded as being important enough to be thought of as a memorable legacy from the 21st Century".
"Legacy is similiar concept as inheritanace and heritage. it is something we inherit from past generations and pass to our future generations. Usually heritage refers to material and economical inheritance, while legacy refers to immaterial and cultural inheritances."
In career, when we talk about a specific manager, a leader, a chief or a CEO, we always remember what he/she is as an overall person, his/her most memorable leadership style, typical ethics and the moral grounds that affect many people around them, that is legacy.
For example, Linchon has a great legacy for his endurance and sufferings, his leadership to the civil war. On the contrary, Nixon has a bad legacy for the Watergate.
And we always hear such lines as: I (we) need to build a legacy for my career/ the company/business.
Hope it helps.