"getter" keyword in @property declaration in Objective-C?

I noticed some code example in Apple's documentation shows the following style when declaring the property:

@property (nonatomic, getter=isActivated) BOOL activated;

I understand it allows you to specify a certain name for your getter method. I'd like to know what is the reason and advantage to use this style.

Will I be able to use the dot notation to get the value (e.g. BOOL aBool = someObject.isActivated)? Or should I use
[someObject isActivated]; to access the property? Thanks!