This is the 16795th most frequent Russian word.
смартфоны
Smartphones.
Here 'смартфоны' is plural in nominative, denoting multiple devices.
Я купил два новых смартфона для своих детей.
I bought two new smartphones for my children.
'смартфонов' is plural in genitive case, used to indicate objects relating to the smartphones.
Где можно найти чехлы для смартфонов?
Where can I find phone cases for smartphones?
'смартфоны' is in nominative plural, used as the subject of the sentence.