Genderless refers to the state of not having a gender. A genderless individual experiences a complete absence of gender. The term is usually interchangeable with agender, but some might prefer it over agender, because genderless more clearly shows that one does not have a gender. Genderless can also be an umbrella for terms like agender, gendervoid, and singularian.
Someone who identifies as agender or partly agender can also use the term genderless since genderless and agender are the same, just that it is commonly used by those who prefer the term genderless, or who collect genders, such as gendercollector and jackdawcollector individuals.
The new genderless flag is based on the agender and non-binary flag. The black stripe represents masculinity and those who are partly male or male-aligned. Purple represents femininity and those who are partly female or female-aligned. White represents a lack of gender and those who only lack some of their gender. And yellow represents androgyny, the non-binary spectrum, and those who are partly a non-binary gender.