It ranges from 1-14, 1 being very acidic (e.g. Hydrochloric acid) , 7 being neutral (e.g. purified water) and 14 being very alkali (e.g. Bleach).
The pH of a substance can be found out by using indicators such as Universal Indicator or by using a pH meter
REMEMBER: WHEN WRITING 'pH', ALWAYS PUT THE p in lower case AND THE H IN UPPER CASE