It's great to have you with us and I'm really glad you joined the forum! I hope you will find it beneficial and enjoy your stay!
As people have explained before, in Islam we refer to everyone as our Muslim brothers and sisters because we have a special bond of faith that unites us like a family. Therefore the first of mankind, Adam and Eve, are often referred to as being our father and mother, because ultimately we are their children (though very far down the line!).
Both our holy book, the Qur'an, and teachings of our last Prophet Muhammad, peace be upon him, teach us to treat each other with respect and behave as one brotherhood:
A verse from the Qur'an reads:
[49:10] The Believers are but a single Brotherhood: So make peace and reconciliation between your two (contending) brothers; and fear Allah, that ye may receive Mercy.
And here follows two sayings of the Prophet, peace be upon him:
It was narrated from Anas (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “None of you truly believes until he loves for his brother what he loves for himself.”
Narrated by al-Bukhaari, 13; Muslim, 45.
It was narrated that al-Nu’maan ibn Basheer said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “The believers, in their mutual mercy, love and compassion, are like a (single) body; if one part of it feels pain, the rest of the body will join it in staying awake and suffering fever.”
Narrated by al-Bukhaari, 5665; Muslim, 2586.
I hope from this, you can better understand the concept of unity that builds the foundation of a Muslim society.
Lastly, please have a look at this thread, which may help you with arabic terms used by Muslims:http://www.islamicboard.com/basics-i...mic-terms.html