All if-else decisions are based on the value of the condition.It is either zero or a non-zero value.
If-else in BF could be achieved by setting a cell to zero/non-zero value.I think an example would do just fine here. Here, let us try printing '1' if value in cell-1 is non-zero ,else '0'. Let cell-2= '0' and cell-3= '1'
[color=#FF0000][>[-]]>.[/color] [color=#008040] #only if cell-1 is non-zero the loop(bracket) will be taken and the next cell set to null[/color]
In general, the first cell would serve as the "condition".