This is the 9370th most frequent Portuguese word.
coberto
Covered.
Here, 'coberto' is used as an adjective meaning 'covered' to describe a physical state.
O prato está coberto com uma tampa.
The dish is covered with a lid.
In this sentence, 'coberto' again acts as an adjective, signifying that the garden has flowers spread across it.
O jardim está coberto de flores.
The garden is covered with flowers.
This usage of 'coberto' denotes the state of the sky being obscured or filled with clouds.