This is the 10047th most frequent Turkish word.
balonun
"Balonun" means "of the balloon" or "the balloon's" in English.
In this sentence, 'balonun' is used in the genitive form, indicating possession - 'of the balloon'.
Balonun rengi çok parlak.
The balloon's color is very bright.
Here, 'balonun' is again in the genitive form, but it establishes a locational relation with 'under'.
Balonun altında oturuyorduk.
We were sitting under the balloon.
'Balonun' still indicates possession, 'the gliding of the balloon', showing subject action association.