Infix operator with built-in evaluation rules.
x y is by default interpreted as Equal[x, y] or x == y.
\[LongEqual] is drawn longer than \[RawEqual].
Used as an alternative to \[Equal].
See The Mathematica Book: Section 1.10.4, Section 3.10.1 and Section 3.10.4.
See also: \[Equal] , \[NotEqual] , \[Congruent] .