This is the 47th most frequent Swedish word.
bli
"To become."
The word 'bli' here means 'become', denoting a change of state or profession.
Hon vill bli läkare.
She wants to become a doctor.
The word 'bli' in this context also means 'become', used to inquire about the outcome or result.
Vad ska det bli av sommaren?
What will become of the summer?
The word 'bli' again means 'become', specifically about developing a personal quality.