VB.NET - Looping

Do Loop:

Do
  statements
Loop While condition

The condition test occurs after the loop statements have been executed,
so statements will always be executed at least once.

While Wend:

While condition
  statements
Wend

The condition test occurs before the loop statements have been executed,
so statements may not be executed at all.  (Depending on the condition.)

For Next:

For counter = x to y
  statements
Next

For Next is used when you know how many time the loop will iterate.

Here's a link: http://www.startvbdotnet.com/language/loops.aspx