Arrangement is when a song idea is put into order, maybe how many verses and choruses it has or if it is music, what sections are connected. An arranger may sometimes develop an intro and a fade-out, ending middle eight, bridge or instrumental section as well. Sometines an arranger helps to develop instrumentation towards a particular style. Arrangement leads rapidly into the music production phase, where the planned instreumentals are actually played in and mixed. In neo-classical forms, when a score is written out, for example, this may be called an arrangement, but if the studio creates the actual track, the instrumentation is referred to as "production".
Arrangement is an important phase which helps to establish the genre and mood of your music. Clearly, arrangement sometimes takes place during the recording process, and so if you are laying down a recording in a particular style, the choice of the recording engineer or producer engineer is critical, as the initial arrangement carries a great deal of power.
Song arrangement and music arrangement is one of my strengths, I'm usually good at developing tracks towards a style, particularly if you can give me examples of other tracks to modelyour song or music on.