ARC and retain ; summary, what is
ARC
All you have to do is claim ownership of any object you need and remember to relinquish ownership when you’re done with it.
retain
The retain method claims ownership of an existing object. It’s like telling the operating system, "Hey! I need that object too, so don’t get rid of it!” This is a necessary ability when other objects need to make sure their properties refer to a valid instance.
Note: retain
re-tain