The Graduate School's online application form includes questions about sexual orientation and gender identity. These are present because it's the easiest way for OSU to comply with Oregon SB 473, which requires public universities to allow students, faculty and staff to identify sexual orientation.
This information is not used to make admission decisions. You are not required to answer them, and omitting this information will not affect your application in any way. Similarly, if you do wish to answer them, your responses will have no bearing on admission decisions.