The legend is linked to thedatabeing graphically displayed in theplot areaof the chart.
Each specific entry in the legend includes a legend key for referencing the data.
What Are Legend Keys?

Lifewire.
Alegend keyis a single colored or patterned marker in the legend.
To the right of each legend key is a name identifying the data represented by the specific key.
This is how you change the text fill, text outline, text effect, and text box.

Lifewire.
you’ve got the option to unlock the legend by simply toggling it on.
Here’s how:
Select your existingchart.
Choose where the legend should be placed right, top, left, or bottom.
There’s also aMore Legend Options>Top Rightif you prefer.