This is the 738th most frequent Hebrew word.
ואילו
"Whereas" or "while."
This usage of "ואילו" contrasts preferences between two subjects.
אני אוהב ללמוד בבוקר, ואילו אבי מעדיף בערב.
I like studying in the morning, whereas Avi prefers in the evening.
This usage of "ואילו" contrasts groups with different preferences.
יש אנשים שאוהבים חורף ואילו אחרים מעדיפים את הקיץ.
There are people who like winter, whereas others prefer summer.
This usage of "ואילו" contrasts two positive attributes of the same subject.