How to isolate between high & low voltage using optocoupler

https://www.newark.com/how-to-isolate-between-high-and-low-voltage-using-optocoupler

" The terms optocoupler and optoisolator are often used interchangeably, but there is a small difference between the two. The differentiating factor is the expected voltage difference between input and output.

• An optocoupler is used to transmit analog or digital information between circuits whilst maintaining a dielectric at a potential of up to 5,000 volts.
  
• An optical isolator is used to transmit analog or digital information between circuits where the voltage difference is greater than 5,000 volts."