Answer 1

The for statement must be follow by a three parts parentheses:

for ( ... ; ... ; ... ) { } // the three three points symbolize expression

The first is called "initialization", because it be executed only once just before the first loop. In general, you set the counter variable to this start value.
The second is a condition, tested on starting each loop, and stop it if it's false.
The third is executed at end of each loop: in general, the counter is modified here.

So, ie:

for ( i=0; i<10; i++ ) {
// do something
}

In the example above, the 'init' set i to zero, and while i<10 the loop will be executed. And after each times the loop "do something", i was increased by one...
Well, in this example the program will do something ten times ( from 0 to 9 -- when i==10, the loop break and don't "do something" )