One of the philosophies in...
One of the philosophies in backpacking is 'Leave No Trace' or 'Pack It In, Pack It Out'. What this means is that you should pack out all of your garbage.
The black plastic bag strapped to the back of the blue backpack contains our garbage.
If you spot someone taking...
If you spot someone taking your picture, =like the group in this picture is doing. It's a nice idea to reciprocate and take their picture.