An adjective is a part of speech used to describe something, which usually goes with a noun or noun phrase, giving more information about the object signified.
English examples include big, good, red, Australian, expensive, wooden, quick.
In English, adjectives usually go before the noun they modify (e.g., a big rock) and there is a certain order in which they should go (e.g., you can’t say *a red big rock).
Other languages have different rules, like where the adjective goes in relation to the noun it modifies, or what order the adjectives go in. Some languages only have a few adjectives.
Don’t assume that the rules for adjectives in another language are the same as in English.