Keybinds are accessed from the F8 menu. These however only include the keys that the Grav team has set. You are able to bind more advanced function to keys using the console.
There is currently no ingame menu-driven way to reset your keybinds to default. As such resetting mistakenly bound keys can be quite difficult, BitMonster have stated that they will be including a reset-to-default button in a future release.
Keys can be rebound from console using the unreal engine 'setbind' command. You To rebind the spacebar key back to it's default, you would run the following command: setbind SpaceBar "Jump | OnRelease JumpReleased"
All the default keybinds can be found in the DefaultInput.ini file in your CAGGame config folder. In most cases: C:\Program Files\Steam\steamapps\common\GRAV\CAGGame\Config
They are in a slightly different format than what you need to perform the command ingame .Bindings=(Name="One",Command="DoHotBar 0") becomes setbind One "DoHotBar 0" So, setbind (Name value) "(Command Value)"