These variants of mouse-1 select entire words or lines at a time. Emacs activates the region around the selected text, which is also copied to the kill ring.
Select the text around the word or character which you click on.
Double-clicking on a character with symbol syntax (such as underscore, in C mode) selects the symbol surrounding that character. Double-clicking on a character with open- or close-parenthesis syntax selects the parenthetical grouping which that character starts or ends. Double-clicking on a character with string-delimiter syntax (such as a single-quote or double-quote in C) selects the string constant (Emacs uses heuristics to figure out whether that character is the beginning or the end of it).
Double-clicking on the beginning of a parenthetical grouping or
beginning string-delimiter moves point to the end of the region,
scrolling the buffer display forward if necessary to show the new
location of point. Double-clicking on the end of a parenthetical
grouping or end string-delimiter keeps point at the end of the region
by default, so the beginning of the region will not be visible if it
is above the top of the window; setting the user option
mouse-select-region-move-to-beginning to non-
this to move point to the beginning of the region, scrolling the
display backward if necessary.
Select the text you drag across, in units of whole words.
Select the line you click on.
Select the text you drag across, in units of whole lines.