Lock phone/pin/phone password

Okay guys, i'm still new to this phone. i've searched on this topic, but nothing really explains the difference between the three? if possible, i'd like to set a password for my phone (like the iPhone?) so even when someone unlocks it from the side of the phone they still can't open my pictures, messages etc. without knowing my password.
when i go to phone settings > security it asks for a password. what is that? do i put whatever i want as my password there? and the pin, why is there a pin1 and pin2
also, on security > change phone password it asks for pin2. why??

SO CONFUSING! a little explanation and help please? i've only had this for a few months.
and i'm afraid of playing around with it too much and the phone gets locked. so better to ask here first. thanks!!

try the next password 1234 or 0000 some of those might work and won't mess up your phone