Shifts in demand curves
Consider a curve with a negative slope (such as the demand function for a normal good).
If you draw a second curve with a negative slope that does not intersect this one then it can either be in the "right-up" or the "left-down" direction from the first.
When they talk about shifts they sometimes just mean this general direction where the new curve will be. Sometimes (as with taxes) there really is a shift.
Let quantity be the vertical axis. If $D(p) = m - \frac{1}{p}$ then an increase in income will shift the demand curve up. But if $D(p) = \frac{m}{p}$ then an increase in income causes something that is not really a shift but a rescaling of the curve. You might still call this a shift up, as by moving up from the original demand curve you will reach the new one.