Deleting old photos from iPhone with iCloud Photo Library on
I've had an iPhone 6 128GB for a couple of years and bought a Macbook Pro about a year ago. I've been running iCloud Photo Library - but not Photostream - and without really looking deeply into the settings exactly, when I take pictures on my phone they helpfully end up automatically in the Photos app on my macbook. When I delete photos from my phone they also seem to disappear from my mac too.
A happy arrangement until I started running low on space on my phone recently. My question is, is my library being 'mirrored' between my devices? IE if I say, delete all my photos from 2012 - 2014 from my phone, will they be deleted from my macbook too? Obviously that would be disastrous.
I guess my question is, what are the best settings to have a situation where my photos will be pushed from my phone to my laptop, but then stored on my laptop indefinitely?
All help much appreciated.