Yes, clutch fluid is the same as brake fluid. Clutch fluid is in the little cylinder beside the brake master cylinder, in the engine bay. It is a hydraulic fluid, and works the clutch basically the same way as the brake fluid works the brakes.
Gearbox oil is an oil, ie lubricant. It allows the gears in the gearbox to work together smoothly. It is not really necessary to replace either the clutch fluid or the gearbox oil just because you are replacing the clutch.
Can I suggest you look at a website "howstuffworks" - something like that.