What's the difference between Do While and Do Until?
Do Until thisBoolean = True... Will keep going "while" thisBoolean is False
Do While thisBoolean = False... Will keep going "until" thisBoolean is True.
What's the difference between IF(A1=B1,C1,D1) and IF(A1<>B1,D1,C1)? Why allow for both?
Rhetorical question. The point is: sometimes you feel like expressing the condition one way; sometimes the other way. And sometimes for good reason.
Suppose you want to continue looping so long as (while) A1=B1 and B1=C1 and C1=D1. It seems straight-forward to write Do While A1=B1 And B1=C1 And C1=D1 ... Loop or simply While A1=B1 And B1=C1 And C1=D1 ... WEnd.
Now suppose you want to loop until A1=B1 and B1=C1 and C1=D1. Isn't it more straight-forward to write Do Until A1=B1 And B1=C1 And C1=D1 than Do While Not (A1=B1 and B1=C1 and C1=D1)?
And potentially, the Do Until expression is more efficient: one less operation. But that depends on how clever the VBA interpreter is.