[linkgoron]

Symbols are used for all kinds of "built in" functions, and they were not "introduced" for this feature. As symbols are unique, they don't break/interfere with existing methods/properties. Therefore, if someone already has a dispose function named dispose, the new feature won't interfere with a method called dispose method and vice-versa.

"Well-known" symbols include things like Symbol.iterator that make "for...of" loops possible, Symbol.asyncIterator for async for loops, Symbol.hasInstance for instanceOf, Symbol.toStringTag for toString, and others.