The control stick, also known as the analogue stick, is the gray stick on the Nintendo GameCube and Nintendo 64 controllers, the white stick on the Nunchuk, the two white sticks on the Classic Controller, and the white or black sticks of the Wii U GamePad and Wii U Pro Controller.
In the Super Smash Bros. series, the control stick has four primary directions that can be input. During gameplay, tilting the control stick sideways will make a character walk in that direction. Tilting the control stick downward will make a character crouch if on the ground or fast fall if the character is airborne. Tilting the control stick upwards will cause a character to jump, but only if the Tap Jump control function is enabled for the player. Inputting a regular attack while the control stick is tilted will result in a tilt attack. The control stick can also be directed in diagonal directions, which will allow for more precise movement in the air as well as allowing some attacks to be angled. Pushing this control stick hard will result in dashing and also increases the power of moves such as Samus's Missile. If outside of gameplay, the control stick can be used to navigate the menu.
On the Classic Controller, the left control stick is used for movement, while the right control stick, analogous to the GameCube C-Stick, is used for smash attacks. When the control stick is pushed in any direction, the pertaining smash attack will be executed immediately.