The console allows running the console commands.
The console has to be enabled in the config.cfg (located at [STEAMFOLDER]\steamapps\common\rocketleague\Binaries\Win32\bakkesmod\cfg\) by setting the following cvar:
cl_console_toggleable "1" //When set to 0, disable console alltogether
To open console press the tilde key (~). Note that the location of that key is locale independent. You can change this using the cl_console_key cvar.