Read CivisRomanus explanation about the difference between using/omitting un: https://forum.duolingo.com/comment/23014358/My-father-is-a-lawyer
No. Solicitors provide general legal services, whilst barristers appear in court (or 'practice at the bar' as it's termed) on behalf on their client. Barristers can only be appointed by solicitors, and not directly by clients. The barristers are the one's you see in courtroom dramas wearing the wigs; judges normally start life as barristers.
Sorry. To answer your question, when someone refers to a lawyer in England, they are technically referring to a solicitor. Just to add to the confusion, barristers are often referred to as 'counsel' outside the courtroom. To be clear, the two roles are quite distinct professions.
Good points. A lawyer, attorney, solicitor, barrister, or legal counsel all act as advocates for a client, acting on their behalf (from Latin 'advocare' to summon someone, to aid you). So in theory any of those job titles should be suitable translations for avvocatto or avvocattessa. Unless Italians use different names to describe specific legal occupations.
"I miei genitori sono gli avvocati" would mean that they are specific lawyers (maybe the only in the room, in the town, or the ones somebody spoke about two minutes before).
You can translate "My parents are lawyers." both as "I miei genitori sono avvocati" and "I miei genitore sono degli avvocati"
(you can consider "degli" as "some", the plural of "un")
i have another wonder: earlier in this lesson there was one saying 'lui fa il conduttore' [e.g.] with the explanation that in Italian they use "fare" for describing the job done; 'avvocato' is also a job - how come here is a different rule? [ok, I understand the social stance someone outlined in the comments before; I'd like to understand from the grammatical pov]
Any profession. You can use "degli operai" (workers), "dei contadini" (farmers), "dei dottori" (doctors). It could also be used in other cases, for example "degli stupidi" (stupids), "delle persone gentili" (kind people). As I said before, it's only an emphatic form, it could also be omitted.
Ok now they changed the translation to "my parents are lawyers." I guess I am just going to have to concede that I really don't know the nuances of Italian enough. I guess I want to be right all the time but the language has many twists and turns that are frustrating for the student. It Is part of the process to be wrong !