what does "for" mean in swift language?

'for', as in probably every language, is used to loop through code multiple times. Swift supports this action in two ways.

In Swift, like in Python, you can use for-in loops. These will loop through a code block once for each item in an ordered collection. These are written as follows:

for item in collection {
    //code to be looped over
}

For example,

for index in [1, 2, 3, 4, 5] {
    print("This has now printed \(index) time(s)."
}

//This has now been printed 1 time(s).
//This has now been printed 2 time(s).
//This has now been printed 3 time(s).
//This has now been printed 4 time(s).
//This has now been printed 5 time(s).

You can also use the more common form of the for loop, which contains an initialization, a condition, and an increment. The initialization runs when the for loop starts. The increment runs at the end of the code block to be looped over (before checking the condition). The condition is checked at the end of the code block to be looped over and if the condition is true, then the code runs from the beginning of code block. In general, a for loop looks like this:

for initialization; condition; increment {
    //code to be looped over
}

And, for a specific example:

for var index = 1; index<6; ++index {
    print("This has now printed \(index) time(s)."    
}
//This has now been printed 1 time(s).
//This has now been printed 2 time(s).
//This has now been printed 3 time(s).
//This has now been printed 4 time(s).
//This has now been printed 5 time(s).

Hope this helps.

ok thanks :D