Basic : C Language if condition

I have a basic question, which is bugging me a lot and I am unable to figure out why a programmer uses it.

    if (0 == Indx)
{ 
//do something
}

What does the above code do and how is it different from the one below.

if (Indx == 0)
{
// do something
}

I am trying to understand a source code written in Embedded systems.