The first thing to realise is that many, in fact the vast majority of priests, belong to no Order at all. Most priests you would see on Sundays, or working in a parish are what are called 'Diocesan Priests'- they are not members of any religious order but simply priests attached to a diocese (hence the name) like Hobart or Geraldton or Rockhampton. As such they promise celibacy and obedience to their bishop but do not take any of the vows of a religious order.
Some priests, however, do choose to belong to a religious order. They have all the obligations of priesthood, coupled with those of their religious order. They take vows of poverty, chastity and obedience, live in religious communities, have their own superiors and would move around quite often and not be confined to a certain diocese. There are many, many different religious orders of priests far too many to all be discussed here.
Elsewhere on our website www.catholicozvocations.org.au you will find a list of the different orders of priests in Australia and some information about them.
That might be a good place to start looking.
Thank you for your question.
A simple answer would be that a brother commits himself to Christ by the vows of poverty, chastity, and obedience. He lives in a religious community and works in nearly any job; teacher, electrician, youth worker, cook, lawyer, technician, parish minister, counsellor, missionary, social worker, university lecturer, just to give a few examples. He tries to live his faith by being a brother to others - by being Jesus in his outreach to the poor, to young people, to those who are searching to grow in their faith, to everyone he ministers too.
A priest's distinctive role is as minister of the sacraments celebrating Eucharist, Baptism, Reconciliation, and so on. He is involved in various other works as well, most often parish-related, but sacramental life is his special ministry. He works with people of all age ranges, again being Jesus in ministering to all people. To a certain extent, the Priest's identity is more involved in representing the 'official' Church, whereas the Brother, although of service to people like a Priest, lives a lifestyle that is more 'alternative', a bit more radical or different - some would say strange or 'a waste'. Certainly, many people might look at Brothers and say they appear fairly normal, just like you and me - why do they live like that?
Maybe there's more to life than just the good things that I'm experiencing at the moment Brothers (and Religious Order Priests) hope that their lives point to our spiritual connection with the Divine, with God, and that others will be drawn to living their own lives more deeply through this witness.
A Brother lives a spirituality that is influenced by the Founder of his particular Religious Order (along with some Priests who belong to Religious Orders as well), and so Brothers live a life that is passionately involved in living the heart of the Gospel - in a way that holds no 'worldly' power or recognition - no authority or special responsibility to the Church's official teaching etc as a Priest might be called to hold to. That is, a Brother is a man just like you, who gives his all to follow his heart and centre his life on Jesus and his gospel teachings. He professes to do this publicly, and for the whole of his life. It's a type of falling in love, but it does involve sacrifice as well, i.e. not being able to follow the path of falling in love with a woman, raising a family, etc.
I hope that my ramblings have some how captured the difference between Brothers and Priests.
Br Rod Thomson fms