VHDL process, nested if statement execution
Here is essentially what the hardware looks like.  The i_ prefix means input or intermediate signal to a register.  What you have is one register for detecting a falling edge on the Switch_1 signal and another register for toggling the LED output whenever a falling edge occurs on the Switch_1 signal.  Note that wrapping the output of a register back to the input through a NOT gate creates a toggle flop.  The toggle flop is enabled (toggles) whenever a falling edge occurs on the Switch_1 signal.