The condition part is checked before each iteration runs. If true, the loop body executes. If false, the loop exits and control passes to the next statement. You write it like a while condition: i < 10, count != 0, x >= limit.
The loop stops as soon as this expression evaluates to false. The condition is checked after the update from the previous iteration runs. If the condition is false from the start, the loop body never runs even once.