The IPA symbol for the “sh” sound in “ship” is [ʃ], the voiceless postalveolar fricative.
To produce [ʃ], the tongue is raised toward the area just behind the alveolar ridge, while air passes through a narrow channel and the vocal folds remain still. That lack of vocal-fold vibration makes it voiceless. English spells this sound most often with “sh,” as in “ship,” “shoe,” and “fashion.”
The sound is distinct from [ʒ], the voiced sound in the middle of “vision,” because [ʒ] uses vocal-fold vibration. It also differs from [tʃ], the “ch” sound in “chip,” which begins with a stop closure before the fricative release. [dʒ], as in “jam,” is the voiced counterpart of that affricate.
The symbol [ʃ] represents a sound, not an English spelling. Other languages may write it with different letters, including Arabic ش, Cyrillic ш, or Albanian “sh.”