What is a spoiler?
Webster-Merriam dictionary defines a spoiler as, "information" about the plot of a motion picture or TV program that can spoil a viewer's sense of surprise or suspense; also : a person who discloses such information'. 1.
In essence, spoiler is anything, in a post, that provides "information"' that you may NOT want every one to see (or for purposes of keeping the view shorter), but if the viewer clicks the spoiler button, they should expect to see something revealed. Example Spoiler Post
[How Do I] Post things into spoilers?
Highlight your text or image(upload first) (see how to upload an image) then click here:
[spoiler]THIS IS MY SPOILER INFO[/spoiler]
Here's a working spoiler: