Dia daoibh, Tá Brón orm agus Tá ceist agam

Elmo

Cén Fáth?

When is possible a better question, but when and why do we use

Dom, Duit....
Liom, Leat ....
Agam, agat .....

Etc.

It is just something that always lost me in Irish class.

thehamo

Dom, duit, do etc: to me, to you to him/her etc. msh tabhair and leabhair dom (give the book to me) seo duit (here you go)

Liom, leat, leis etc. With me, with you, with him/her etc. Msh thóg mé mo chara liom ( i took my friend with me) is liomsa é (i own it)

agam, agat, aige etc, I have, you have, he/she has etc msh tá dhá Euro agam ( i have 2 euro)

Elmo

And orm?

Krusader

orm, ort, air, uirthi - on me, on you, on him, on her
tá áthas orm, im happy - theip orm, i failed - bhí tú ag féachaint air, you were looking at him

Heres some links
http://www.daltai.com/grammar/pp.htm

http://www.daltai.com/grammar/ppsam.htm

Elmo

And does this happen in other languages where the prepositional pronoun is attached to the person (owner).

Krusader

Most of the Celtic languages they do and i think Spanish in some cases