docs: revised 02_Loops.md

revised the text, split into sections

Author: p7nov

examples/02_control_flow/02_Loops.md

@@ -1,6 +1,10 @@
 #Loops
 
-### for, while, do-while
+Kotlin supports all the commonly used loops: `for`, `while`, `do-while`
+
+### `for`
+
+`for` in Kotlin works the same way as in most languages.
 
 <div class="language-kotlin" theme="idea" data-min-compiler-version="1.3">
 
@@ -19,7 +23,11 @@ fun main(args: Array<String>) {
 
 </div>
 
-1. Loops through each cake in the list
+1. Looping through each cake in the list.
+
+### `while` and `do-while`
+
+`while` and `do-while` constructs work similarly to most languages as well.
 
 <div class="language-kotlin" theme="idea" data-min-compiler-version="1.3">
 
@@ -46,13 +54,13 @@ fun main(args: Array<String>) {
 
 </div>
 
-While and do-while constructs work similarly to most languages.
-
-1. Performs the block while the condition is true.
-2. Performs the block first, and then loops while evaluating the while condition.
+1. Executing the block while the condition is true.
+2. Executing the block first and then checking the condition.
 
 ### Iterators
 
+You can define own iterators in your classes by implementing the `iterator` operator in them.
+
 <div class="language-kotlin" theme="idea" data-min-compiler-version="1.3">
 
 ```kotlin
@@ -78,10 +86,10 @@ fun main() {
 
 </div>
 
-1. Providing an iterator implementation (marked with operator modifier).
-2. Returns the iterator for the list, which meets the method requirements
-    1. next(): Animal
-    2. hasNext(): Boolean
-3. Loops through each animal in the zoo
+1. Defining an iterator in a class. It must be named `iterator` and have the `operator` modifier.
+2. Returning the iterator that meets the following method requirements:
+  * `next()`: `Animal`
+  * `hasNext()`: `Boolean`
+3. Looping through animals in the zoo with the user-defined iterator.
 
-The iterator can be declared on the type or as an extension function.
+The iterator can be declared in the type or as an extension function.