What does the quote a tree is known by its fruit mean?

You will be known for the good you do for others.

What you are known for depends on what others value in you and need most from you. This applies to all service roles in your life, you as a parent, as a teacher, a worker and so on.

The important aspect of the phrase is that this holds whether you like it that way or not.

An Apple tree is named after the good fruit it provides us. Since the fruit is so juicy, sweet and nutritious, the tree's shape or size and the quality of its wood take on a secondary role.... whether the tree likes it or not.