Why the video didn't mention %s? and what is it?

%s is what we refer to in the programming community as a String Format Specifier. The printf statement basically means "print formatted" and its value is a string (that contains these String Format Specifiers) followed by variables or values that relate to the String Format Specifier, in the same order as the specifiers themselves.

%s is the String Format Specifier -

Here is an example below

char [] name = "Dane";
printf("My name is %s", name)

//output -----> My name is Dane

Another example with numbers the String Format Specifier for integers is %d, notice how the variables after the string are in the same orders as the modifiers, and notice how we can input a value for a String Format Specifier variable instead of a variable itself?

int age = 19;
char [] name = "Dane";

printf("My name is %s and I am %d years old, I am part %s and %s, and am a proud high school graduate from class %d", name, age, "Jamaican", "Bahamian", 2013);

//Output ---> My name is Dane and I am 19 years old, I am part Jamaican and Bahamian, and am a proud high school graduate from class 2013

If you still don't understand or want to ask any questions feel free to ask, I or others will be happy to respond!

P.S Excuse the syntax, its been a while since I used Objective-C, if I am wrong with syntax, I will fix it.