Interfaces are basically class declarations that reveals the accessible properties and methods. A sample interface for Class car is shown below.

/* Every class interface starts with 
@interface keyword followed by class name. 
NSObject is the root class of all classes.
@interface Car:NSObject
    // Instance variable
	int modelNumber;
// Properties declaration
@property(nonatomic, strong) NSString *modelName;

// Method declaration
- (void)start;
/* Every class interface ends with 
@end keyword.