Green boxes which I have drawn depict 'gaps' (difference between the closing price of one period and the opening price of the next period). These prices are controlled by Market Makers. On NYSE, there is only one specialist per listed stock . On Nasdaq, there can be numerous market makers for the same stock , or just 2 to 3. More liquidity, more market makers. Typically the firm (or the group of firms called "syndicate") who takes that company public ( IPO2.21% ) will serve as the market maker for that stock after it is traded in the open market).
Price flow should be orderly however market makers commonly gap up stocks (by varying degrees) nowadays for numerous reasons (mostly on devious agenda i.e. to jump over fib hurdles, catch stop orders etc).
Gaps naturally always get filled. It is not a matter of IF but WHEN. Sometimes it can take days, sometimes months.