How to highlight all occurrences of a word in an Emacs buffer?

Question

Notepad++ has a convenient feature: if you select a word in your text (not necessarily a keyword), the word is highlighted throughout the text. Can this be done in Emacs as

Answer 1

Light-symbol will highlight whatever symbol point is over.

Alternately, you can use occur, which lists all lines matching a regexp. It's useful to quickly see all functions in a class.