Adjectives are words which describe nouns, and they have to agree with what they describe. This means that the form found in a dictionary (ending in -o or -e) changes its ending depending on whether what is being described is masculine or feminine, singular or plural.
Adjectives ending in -o have four forms altogether:
Adjectives ending in -e have only two forms:
Unlike in English, adjectives in Italian go generally after the noun.
masculine - feminine
singular - plural