Need a little help understanding the code

Hey, can someone explain this piece of code to me which i got from the book?

[code]#import “BNRPerson.h”
@class BNRAsset;

@interface BNREmployee : BNRPerson

@property (nonatomic) unsigned int employeeID;
@property (nonatomic) unsigned int officeAlarmCode;
@property (nonatomic) NSDate *hireDate;
@property (nonatomic, copy) NSArray *assets;

-(double) yearsOfEmployment;
-(void)addAsset:(BNRAsset *)a;
-(unsigned int)valueOfAssets;

I get the part where we say that there is somewhere an NSArray with a pointer named assets.

What i dong get is the last two lines, what are we doing with void and where is the AddAsset from and do i understand correctly that we are just creating a method called valueOfAssets that returns an unsigned int?

Thank you

The line:
-(void)addAsset:(BNRAsset *)a;
defines a method that will add BNRAsset to a NSMutableArray. The implementation can be found in the .m file.
Since this method does not return any value it is (void)

-(unsigned int)valueOfAssets;
defines a method that calculates the value of the assets from the mutable array defined earlier.
It returns a integer.

I hope this helps.