Typically an emoticon, meaning bubbling, floating, repeating or evincing hearts. Sometimes used as cat ears and mouse ears with a colon.

It could also be a keyboard mashing or mathematical expression.

In religion, there are those who believe that it is one of the most important "Angel Number" which can be found with a simple search. Since 3 is the quintessence of the trinity, its groupings 3, 33, 3333 and 33333 (or 3.3333) are alleged by many who subscribe to the beliefs associated with the trinity, that it is a good sign from angels, that "the ascendant masters" are giving you direction.

Retroflexed convergence of math and religion occurs with the trinity and 33, which is the sum of the first 4 factorials, multiplied by the mark of the beast, sequences of 6 of the same size but with the last digit 7 the result is a sequence of 1s. 3n x 3n 6n-1_7^1 = 111111111111111.

Grouping Breakdown
Side 1
3 3333 - Trinity of Angels, and n 3s

Side 2
3 3333 - Trinity of Angels, and n 3s
6 6667 - Subtended (for comparison to evil, 666) Mark of the Beast with Trinity, 3, added to the number of digits n. 3+n=3+4=7.

Expressions
33333 x 3333366667 = 111111111111111

There are whole websites dedicated to the beliefs behind this and many other "Angel Numbers" and are not academically-based. However, to each his/her own.

When you eat dirt for the first time and leave your family to build a shack in the woods