This is the 106th most frequent Catalan word.
unes
"Unes" is the Catalan feminine plural indefinite article, meaning "some" in English.
In this sentence, 'unes' is used as an indefinite article in plural feminine form to refer to an unspecified quantity of a feminine noun ('aus').
Vaig veure unes aus al parc.
I saw some birds in the park.
'Unes' here is used as an indefinite article in plural feminine form, indicating an unspecified group of feminine subjects ('persones').
Unes persones creuen que és una bona idea.
Some people believe that it is a good idea.
In this sentence, 'unes' is again an indefinite article in plural feminine form used to describe an unspecified pair or number of feminine items ('sabates').