At example: On se odselio iz Srbije. means that he left Serbia On se preselio u Srbiju. means that he came to live in Serbia. But when we just say: On se odselio. or On se preselio. it has the same meaning.

Steve, the meaning of the verb ODSELITI (se) could be your English to LEAVE, and PRESELITI (se) your MOVE. You are free to contact me if you have more questions. Kamenko

Odseliti se means to move away. Preseliti se means to move away to another place: to change dwelling. In practice, they mean the same and they are used interchangeably. It's the emphasis that changes: In the first verb the emphasized meaning is that somebody went away, and in the second that they changed their dwelling place.