Questions & Answers about Они обсуждают брак.
Они means they. It is the 3rd person plural pronoun.
So in Они обсуждают брак, the subject is they — some group of people who are discussing something.
A useful note for English speakers: Russian pronouns change for case, but here они is in the nominative case because it is the subject of the sentence.
Обсуждают is the verb обсуждать in the present tense, 3rd person plural.
Breakdown:
- обсуждать = to discuss
- обсуждают = they discuss / they are discussing
The ending -ют shows that the subject is they.
So:
- я обсуждаю = I discuss
- ты обсуждаешь = you discuss
- он/она обсуждает = he/she discusses
- они обсуждают = they discuss
In this sentence, the verb agrees with они.