The 3DS is a system by Nintendo released in 2011. The system was a sequel to the DS(i) which introduced 3D graphics without the need of eyewear.
There were many models shipped throughout the world.
This is the first kind of system. It looks more like a DSi than the other models.
2DSs were released in 2013, and don't fold. Instead, you flip a little switch. The layout is completely different to 3DSs.
New 3DS/2DS XL
A New 3DS/2DS XL looks more like an original DS. It also adds ZL, ZR and a C Stick, but games rarely use them. The new Internet Browser's media player uses the latter to ramp up and down in speed.