This is the 3543rd most frequent Russian word.
саду
"Саду" translates to "garden" in English (in the dative/prepositional case).
The word 'саду' is in the prepositional case, used to indicate the location where the action is happening (in the garden).
Я гуляю в саду.
I am walking in the garden.
Here, 'саду' again is in the prepositional case, referring to the location where something exists (in our garden).
В нашем саду растут красивые деревья.
Beautiful trees grow in our garden.
In this sentence, 'саду' is also in the prepositional case, used to specify the place associated with an activity (in the garden near the house).