find the equation and build the place geometric

1) located 4 units of the x axis

I do not understand. The answer is a cylinder of equation: $\displaystyle y^2+z^2-16=0$

As located 4 units of the x axis can form a cylinder?

2) located 3 units the front of the plan yoz and the 5 units up the plan xoy

The answer is a straight x=3; x=5. As i build the place geometric?