Can you explain some syntax to a non-python person?

Not a python coder here. Can someone please explain (or even better link to something that explains) the bit in red.

MyVar = line.split()[3][B][COLOR="#FF0000"][4:-1][/COLOR][/B]

It is the slice operation (or substring) of a String.
The red bit will return the 5th char to the to 2nd last char. (as everything is indexed from 0).

You can read through