Hello, and welcome back!
One that turns in the opposite direction is a gear diff. They have oil in that you can change the weight of to alter how the car reacts on track. Normally used in high grip situations like carpet and dry astro.
One where they turn the same way is a ball diff. The pressure on balls can be adjusted using a hex or screw in one of the outdrives - you will see this if you remove the drive shaft. Normally used in low grip conditions like wet astro, dirt, wet grass.