It commonly represents the unaspirated voiceless bilabial plosive /p/, like the pronunciation of ⟨p⟩ in "spin".
[1] The name of Pe in the Early Cyrillic alphabet was покои (pokoi), meaning "peaceful state".
The capital Cyrillic letter Pe looks exactly like the Greek capital Pi from which it is derived, and small Pe looks like a smaller version of the same, though with a less prominent horizontal bar (Greek Π π > Cyrillic П п).
The lowercase forms, however, differ among the languages that use the Cyrillic alphabet.
In handwritten Serbian, however, it appears as a Latin U ⟨u⟩ with a bar over it ⟨ū⟩.