R18 - To be shown only in
specially licensed cinemas, or supplied only in licensed sex
shops, and to adults of not less than 18 years

15 rating – Suitable only for 15 years and over

12A/12 – Suitable for 12 years and over.
or contain material which many parents will find unsuitable
for them.

The ‘12A’ category exists only for cinema films. No one younger
than 12 may see a ‘12A’ film in a cinema unless accompanied by
an adult 

 18 rating - Suitable only for adults

 PG Parental Guidance – General viewing, but some scenes may be unsuitable

Universal - Suitable for all.