This option controls whether the client should launch minimized. With the option enabled, the client will start minimized and you have to open it from the task bar to make view it and select a server. With the option disabled, it will instead launch with the window open.
While launching minimized, the client can still establish a connection. This option is best used in combination with Launch on startup and Connect to OVPN when client starts for a smooth startup experience to have it automatically launch and connect in the background.