What is "1 hot *"

Sorry to ask such a basic question but I have come across the notion of “1 hot someting” several times in the specialization. I don’t understand at all what this is about.
Here is an example:

Thanks for your help

Hi @Pierre_BEJIAN , we use one-hot encoding to encode a categorical variable into multiple binary variables. For “Gender”, it can include “male”, “female”, “transgender”, “gender neutral” and more, so when you encode this variable, for each category value it forms a binary variable such as “is_male”, “is_female”, “is_transgender”, “is_gender_neutral” and so on. Each of the binary variable can take a value of 0 or 1.