This is the 3756th most frequent Russian word.
цветами
"Цветами" means "flowers" (instrumental plural form).
In this sentence, 'цветами' is the instrumental plural form, indicating that flowers are the means by which the table is being decorated.
Мама украшала стол цветами.
Mom was decorating the table with flowers.
Here, 'цветами' is the instrumental plural form, used to describe the means or tool for the admiration.
Мы любовались цветами в саду.
We admired the flowers in the garden.
In this usage, 'цветами' represents the means by which the painting was created, specifically referring to colors.