This is the 1365th most frequent Russian word.
мария
"Мария" is the Russian form of the name "Maria," a common female given name.
Here, 'Мария' is a proper noun used as the subject of the sentence.
Мария любит читать книги.
Maria likes to read books.
In this sentence, 'Марию' is the accusative form of 'Мария', used as the object of the verb 'видел' (saw).
Я видел Марию в парке вчера.
I saw Maria in the park yesterday.
Here, 'Марии' is the prepositional case of 'Мария', used after the preposition 'о' (about).