Hyphens

What is it?

U+002D - HYPHEN-MINUS

Every keyboard I've ever seen has a hyphen key on it, so this shouldn't be a problem.

To link words together, as in "wolf-person", or
to add prefixes to capitalized words, as in "un-American", or
to break words (at syllable boundaries) over multiple lines, in a block of justified text.

U+2013 – EN DASH

To specify ranges, as in "1974–1976", or
to link a more than one word to another word, as in "computer science–related", or
under some style guides, to link clauses together, as in "She who might have swayed society's circle with the sceptre of nobleness – she who might still have shared in the greatness of her position and defied the crooked stream of poverty in which she so long sailed – had she only been, first of all, true to self, then the honourable name of Sir John Dunfern would have maintained its standard of pure and noble distinction, without being spotted here and there with heathenish remarks inflicted by a sarcastic public on the administerer of proper punishment; then the dignified knight of proud and upright ancestry would have been spared the pains of incessant insult, the mockery of equals, the haunted diseases of mental trials, the erring eye of harshness, and the throbbing twitch of constant criticism." Note the spaces around the dash in this case.

U+2014 — EM DASH

Under some style guides, to link clauses together, as in "The Howden Estate, on which are elegantly formed two buildings of note—namely, Blandford Castle and Lauderdale Lodge, both exquisite constructions of architecture and skilled workmanship, and occupied respectively by Sir Sydney Hector and Admiral Charles Depew—lies chiefly around the south-west of Yorkshire, and is not quite so desirable or adapted for agriculture as the two first mentioned, being mostly rented for grazing purposes by the numerous and varied owners of its rugged plots."

U+2212 − MINUS SIGN

Everybody seems to think a hyphen works fine for this ;_;

GNU+Linux: Left control + Shift + U, then 2212. No, I don't know why there's not a compose sequence for it.
MacOS: this nonsense
Windows: …there's probably a way, I just don't care enough right now to figure it out right now

When writing negative numbers, as in "−42", and in subtraction expressions, as in "50−8". The hyphen generally suffices for this.