Output/Execution location is defining where is the code Block is going to be executed or outputted. So that when CJT is preparing the code Blocks it then wait for WordPress signals where those code Blocks should be executed. Currently CJT is using two Location. Header and Footer locations. Header location is being fired by WordPress via wp_head and admin_head hooks for Frontend and Backend sides respectively while Footer location is being fired by WordPress via wp_footer and admin_footer hooks for Frontend and Backend sides respectively.
Blocks executed in the Header location would got their outputs between the HTML <head></head> TAG while Blocks that uses Footer location are going to get outputted just before </body> tag closing tag.
So it would be very handy in many cases to switch between those location based on the script you create. Some Blocks might required some other scripts to be loaded first so they wait at the end/Footer while other those doesn’t require any restriction or need to take a higher priority would use the Header location.
There’re many other Location in the features queue that CJT would include in the next releases. There would a huge number of location that would serve most of the cases that CJT users might need.
NOTE: Hook location has no effect when delegating Global Block with Shortcodes! Using Shortcode for delegating Block would result of output/execute the code Block exactly in the point where the Shortcode is added.