I'm not sure if this is universal or Mac-specific. Alt+arrow moves the cursor one "word" at a time. What's considered a "word" is a different and a somewhat difficult topic, but whatever the word is, it should be consistent in all directions.
But it's not!
If I do X jumps forward and X jumps backward I might end up in a different position, not the one I started in. Thanks to quotation marks and other symbols that break the consistency of words' borders.