What the up arrow means
The up arrow ↑ is the plain, thin version, officially called upwards arrow (U+2191). It is used to say "increase" (prices ↑), "see above" or "this" (↑ pointing at the previous message), and to show an upvote. ⬆︎ is a bolder black arrow that also works as the emoji ⬆️, and ⇑ is the double up arrow used in math and logic.
Arrows have exact meanings in a few fields. In chemistry, ↑ after a product means a gas is released. In math, Knuth's up-arrow notation writes a ↑ b for a to the power of b, and a ↑↑ b for repeated exponentiation. In phonetics, the small raised arrows ꜛ and ꜜ mark upstep and downstep in tone languages.
Keyboard arrows: ⇧ Shift and ⇪ Caps Lock
Apple keyboards and macOS menus label keys with symbols. The hollow arrow ⇧ (upwards white arrow) means Shift, so ⌘⇧4 means Command + Shift + 4. The arrow from a bar ⇪ means Caps Lock. Many Windows keyboards print the same ⇧ on the Shift key.
Watch out for look-alikes: ⌃ (up arrowhead) is the Mac Control key, not an arrow, and ^ is the caret on your keyboard. The triangles ▲ and 🔼 mean "up" in sort buttons and media controls, while ⏫︎ means fast up. For more triangle shapes, see the triangle symbol page.
How to type the up arrow ↑
On Windows, hold Alt and type 24 on the number pad to get ↑, or Alt + 30 for ▲. On a Mac, open the Character Viewer with Control + Command + Space and search "up arrow". On iPhone and Android, search "up" in the emoji keyboard to find ⬆️ and 🔼.
In Microsoft Word, type 2191 and press Alt + X. In HTML, use ↑ for ↑ or ⇑ for ⇑. In LaTeX, use \uparrow or \Uparrow. For the opposite direction, see the down arrow symbol, and for every direction at once, the arrow symbols page.