How to let a GameObject move?

Hello i forgot how i write a simple line of code that let the gameobject move .
it was like this.

Rigidbody.velocity = 20

See the scripting reference.

First, you need to address the actual rigidbody component on your object, not the rigidbody class. In a script this is done with the lowercase classname, i.e. rigidbody.

Second, velocity is a 3D vector. If you want to change it, you must set it to another 3D vector - either by assigning a new one or by modifying the old one through multiplication etc.

So, your code should look something like this:

rigidbody.velocity = Vector3(0,10,0); // set object to move up
rigidbody.velocity *= 4; // make object 4 times as fast

If your game object has a Rigidbody, you may set its velocity directly - but remember that this is a velocity vector, a Vector3 defining whose length is the absolute speed. If you want to put a rigidbody to move in its forward direction, use this:

rigidbody.velocity = transform.forward * 20;