A traditional shotglass measures 1.5 ounces (not 1 ounce).
In the US, A "pony shot" or a "short shot" is 1 ounce.
Some shotglasses are 2 ounces with a measuring line
at the 1.5 ounce mark.
People usually use shotglasses to drink hard liquor
although if someone is REALLY drunk, sometimes they're just used to trick them into drinking water or fruit juice.
Depending on a person's tolerance
, 1 shot could get someone buzzed
, 2-3 shots perceivably tipsy
, and anything beyond that probably drunk
For snorting Vodka from an upside-down shotglass, see chilly willy