Location: Oregon Rainforest
can you be more specific about the "change" he makes to the front suspension?
you may just be watching an air pressure check. or minor adjustment for conditions expected on the ride...
Location: Noosaville, Sunshine Coast, Australia
In the simplest terms, if he's going uphill, he tightens it, though he doesn't always lock it, it depends on the hill and terrain, and if he's going downhill again, terrain and slope, he'll release it.
Level surface depends if on a flow track or fire trail to where he positions it.
Location: Parañaque, Philippines
I think your friend is just locking the suspension during climbs so his bike doesn't experience "pedal bob power loss" on the climb, I put air quotes because that term changes a lot between countries, it basically explains that if you have a front suspension and you are climbing, your bike will have a tendency to bob up and down while you're pedaling which a lot of people actually generally say eats up the force you need while climbing up. Here are a few pointers
1.) power loss thru the suspension moving up and down has been debunked by using a power meter and a record of climb times on various tests, it was actually observed that keeping the suspension open lets you climb faster because it produces more traction for the bike hence it actually meant more power was also transferred to the forward momentum of your ride
2.) leaving it on open mean you experience less road/trail chatter that transfer to your hands thus helping you make more runs downhill during the ride
3.) closing it offers no benefit at all
now to answer your question about suspension settings, various companies equip their forks with minimal settings all the way to very complicated set ups (ex: rebound, sag, psi, etc etc.) these settings need a whole thread for explanation and I think words wouldn't be sufficient to describe the feeling you get for each setting but there really is a night and day difference between these and to better figure it out, it is best to consult your trusty bike mechanic or toy around with it your self, there is no one way to dial these settings in as it all really boils down to how you use your bike and how rowdy the trails your riding at is
hope this helps and enjoy!