In Composer, a part is a set of one or more staves throughout the song, that are view or printed together. In the simplest case, a part is for a solo voice or instrument for which the musician plays from only one staff at a time, such as an oboe or saxophone. Another case is a part for a keyboard instrument that has two staves for the right- and left-hands. In Composer, the conductor's score, which shows staves for all of the instruments and/or voices, is treated as a part.
A part can be formatted and paginated independently of each other, and independently of the formatting of the conductor's score.
A given staff can be displayed in more than one part. For example, usually a staff is shown in both the conductor's score and a separately formatted part for just that instrument.
All of the parts of a score are integrated so that if you, for example, add a note to a staff that appears in more than one part, the note is automatically added to all of the parts. If you add a note in the conductor's score, that note also shows up in the instrument part that the staff belongs to. Or, if you add a note in the instrument part, that note will automatically show up in the conductor's score.
If you have not done so yet, it is highly recommended that you read the topic Understanding Staves, Staves, and Parts.
This section on Preparing Parts is organized as follows: