What is Lorentz symmetry,what is symetrical and what is it relative to?

Answer 1

Symmetry means that you have done something to an object and it still looks the same.

In Lorentz symmetry, your objects are the laws of physics, described by equations. What you do to these is subject the variables (position, time) in them to transformations (called Lorentz transformations) which are the result of looking at them in one reference frame or another. The symmetry is that the laws of physics come out the same: the equations have the same form. This means that the physical laws are invariant (even though the quantities like position and time get changed).