I used to invest back in the day. Anyway, there are many investing strategies. They all have names such as Value, Growth, Event Driven, etc. I won't list them all. The investing strategy that attempts to exploit movements in stock price after an event (e.g. the type that you are asking about for the earnings announcement in the Tesla example) is called "Event Driven" investing. Another example of an "event" would be after an acquisition is announced to the public. Typically the target (one being acquired) stock will go up and the acquiror (one acquiring) will go down. Investors often try to take advantage of this trend. What is the relationship that investors are betting on if the target price always (usually) goes up, and the acquirer going down? Closing risk. At any point the acquisition, despite being publicly announced, could fall apart because of due diligence issues, etc.

Relating all that back to your question about Tesla: the fundamental value or true value of a company may or may not be reflected in a company's stock price. Think of the stock market as a manifestation of what people (investors) might believe the value is, but the reality is that the fundamentals might be vastly different. The reversion back to norm is something that happens as the market (investors who are imperfect--trust me--think AIG, Bear Stearns, Lehman) attempts to settle on true value.

Side note: Volatility in the stock price could also be attributed to a small float (not that many shares outstanding which leads to a small number of investors causing spikes in the price), but I'd have to look at Tesla's stock info to be certain.

Hope this helps,

Jenny