What is structured programming?

Structured programming was the last big trend before object oriented programming. The idea is that your programs should have a bit of a structure - subroutines, if-else blocks, while, for loops, etc., instead of just doing everything with GOTO (like the computer actually does it).
If you have written GOTO based code (say, in BASIC or something), the benefits of structured programming will be obvious to you.
There are no “unstructured” programming languages in popular use today, except if we count assembly .