Sexual orientation refers to your sexual and romantic thoughts, feelings, and attractions (or lack thereof) to other individuals. Who you do or do not have sex with does not determine your sexual orientation. For example a person who has never had sex (i.e. a virgin) still has a sexual orientation; if they are attracted to the opposite sex they are heterosexual, if they are attracted to the same sex they are homosexual, if they are attracted to both they would be considered bisexual or pansexual, and if they are not sexually attracted to anyone then they would be asexual. This orientation does NOT change by them having or not having sex with anyone.
Bare in mind, a person's sexual orientation is separate from their biological sex (male, female, intersexed) or what gender they or society identifies them as (man, woman, third gender or other).
LGBTQ is an acronym which stands for Lesbian, Gay, Bisexual, Transgender and Queer or Questioning. This acronym is often used in the media and common speech as a blanket term to refer to all sexual and gender expression minorities even if they are not expressly mentioned in the acronym (ex: Asexuals).