So we're explaining this abstract statement:
SIMILAR TO '(X|Y)%'
SIMILAR TO means to match the following pattern, which can include regular expressions. (LIKE uses simpler pattern matching, = checks for identical strings.)
The ()s match in this case just one character: X|Y. The | means "or", so if the string starts 'X' or 'Y' we're good so far.
% is a wildcard, matching literally anything else. So any string that starts X or Y will count. These strings will match: Xander, Yellow, XYZZY. These strings will not match: x, yup, bing blang blaow.
I hope that clarifies? :)
