If, if-else and if-elif-else statements, and why the order of elif conditions matters

Conditional statements let a program choose what to do based on data. The simplest form is if: a header line with a condition and a colon, followed by an indented block. If the condition is true, the block runs; if not, Python skips it and carries on after the block. Without conditionals every program would do exactly the same thing every time, whatever its input.