What are some things that causes stocks to go up or down a lot in one day?

Buying & Selling are the only two things that move stock prices... everything else affects these two things.

Earnings or dividend announcement is higher or lower than expected.

Lawsuit opened or closed.

Problem with the product (product recall, food poisoning, etc. depending on the type of company)

Change in company management

Natural disasters that disrupt production (e.g. Hurricane Maria caused a shortage of hospital supplies)

Political turmoil (Brexit, threat of war in Korea, etc.)

algortithms (like ones which pump up a sector and dump another sector) or sales announcements (earnings releases)

computer trading algorithms

humans following the herd mentality

SPECULATING ACTS BY TRADERS IN THE WORLD AND ALSO ARE CONTROLLED BY PRESET TRADE SOFTWARE THAT IS TRIGGERED BY PRICES.

Big shifts are caused by supercomputers which take advantage of quick moves in direction. These computers can feed on each other which exacerbates the situation. Stock prices are determined by two things - logic and emotion. Logic dictates that companies, on average, have physical assets and make a moderate income from using those assets. Emotion results in the price being bid higher or lower than logic dictates.

news or the reaction to it https://youtu.be/UQEsAr9pybY ridiculous!

Bad news, good news, world events.

Profit taking, Paranoia, Program Trading, and New Facts.

the rich fleecing the gullible punters Cesar