All-gender pronouns are inclusionary terms that are gender-neutral. This means that they are not associated with a social gender. These terms do not imply male or female, and can be broadly used to simply define personhood instead of gender. All-gender pronouns are important when it comes to the multiplicity of gender identities that a person is experiencing or identifying with or when one is unsure of a person's gender identity.
More About All-Gender Pronouns
All-gender pronouns can also be viewed as gender-neutral pronouns. Instead of dividing English pronouns into male and female, all-gender pronouns encourage a broad encompassing of personhood in non-gender identifying language. This helps those transitioning or those who don't fit neatly into either "he" or "she" to feel included.
There hasn't been a consensus on what all-gender pronouns should be. Some common gender-neutral pronoun uses include using "they" instead of "he" or "she," or the use of "ze" to replace "he" or "she" and "zir" to replace "his" or "her."