Police Community Support Officers (PCSOs) work with police officers and share some, but not all of their powers. Special constables are volunteers who have the same powers as police.
PCSOs
A PCSO can, for example:
give someone a fixed-penalty notice, eg for littering
demand the name and address of someone being anti-social
take alcohol off a person aged under 18
A PCSO can also ask a police officer to arrest a person.
The power of PCSOs can differ between police forces (external link).
They must wear a uniform clearly marked ‘PCSO’.
Special Constables
Special Constables are volunteers but have the same powers as police officers.