The hyphen, "-", is a punctuation mark used to join words and to separate syllables of a single word. Son-in-law is an example of a hyphenated word. There are two related symbols: the em dash "—" and the en dash "–". The en dash, like the hyphen, has a relatively limited use—connecting dates, like 1945–47. The em dash, as I used in the previous sentence, is likely the symbol you want to learn more about. Since the em dash isn't available on most keyboards, it will often be substituted with a hyphen. For those who do want to use it, many word processors will automatically insert an em dash when you type a pair of hyphens.

The em dash is perhaps the most versatile punctuation mark. Depending on the context, the em dash can take the place of commas, parentheses, or colons—in each case, to slightly different effect. It can also be used to indicate missing portions of a word, though less often. In your example you correctly used the em dash in place of a colon: here, it emphasizes the conclusion of your sentence. Typically, however, an em dash is not surrounded with spaces and one would not capitalize the first letter of the following sentence. 

Here are three more examples, using em dashes in place of commas, parentheses, and to indicate missing portions of a word, respectively. Notice how in each case the em dash is more emphatic and intrusive compared to its counterpart

1. Alice walked briskly through the room, doing her best to ignore Jim—who was staring daggers at her—when she bumped into Stacy.
2. It was not until John picked up every fallen stick—all 74 of them—that he finally began to calm down.
3. Mr. K—— testified that the defendant yelled "F—— you!" as he pulled the power plug.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence