Hello Ssonbol,
Thank you for sharing your question with the Arduino community.
Find answer to your question below:
After you upload a sketch to the board, that sketch will keep running constantly as long as the board has power. When the board is connected via USB to the PC it receiving power through the cable.
If you want your board to be cordless you can power the board with a battery either through the power input jack or VIN Pin. Please check the voltage you apply to the board is within the recommended range: For UNO WIFI Rev2 recommended: 7 - 12V.
I hope this was useful!
Good luck with your projects!