This is the 26th most frequent Czech word.
byla
"Byla" means "was" (feminine singular past tense of "to be").
In this sentence, 'byla' is utilized to describe a past characteristic or ability, showing agreement with the feminine singular subject 'Ona' (She).
Ona byla velmi dobrá v kreslení.
She was very good at drawing.
Here, 'byla' introduces a past temporal clause describing her state in the past, linked to her actions in that time.
Když byla mladá, cestovala po světě.
When she was young, she traveled around the world.
The word 'byla' is used here as the past tense singular feminine form of the verb 'být' (to be) to indicate a state or condition in the past.