Even though many people get gender and sexuality mixed up, there is a distinct difference between the meanings of these two words. Gender refers to whether the person is a male or female. It does not have anything to do with whether they prefer men, women, or both as their partners or who they are attracted to.
Sexuality refers to whether you are homosexual, bisexual, or heterosexual. It refers to which gender of people you want to be with sexually. You can be any gender with any sexuality. Often on applications, it will ask you your gender. Then you will label it male or female. It will most likely not ask you about your sexuality because it does not pertain to the job.