What is a "tell block"?

Applescript FAQ Core Language
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#1

Usually, we call “tell block” to any code within “tell”-“end tell” statements, when “tell” is targeting an application. This is a “tell block”:

tell application "Finder"
	empty
end tell

Here, we tell the Finder to empty the trash.

And this is also a “tell block”:

tell application "Finder" to empty

And this is not a “tell block”:

set x to {2, 45, 72}
tell x
	item 2
end tell

Here, the variable “x” is an AppleScript object (a list), not an application; so, we don’t consider this a “tell block”.