A label is a simple widget for displaying a single line of text. An example of creating an instance of a label is
label .l -text "Hello world!"
which simply creates the label named
.l with the text `Hello
world!' displayed in it.
Most widgets that display text can have a variable associated with them
through the option -textvariable. When the value of the variable
is changed the text changes in the associated label.
label .l -text "Hello world!" -textvariable mytext
creates a text label called
.l displaying the initial text `Hello
world!' and associated text variable
mytext will start
with the value `Hello world!'. However, if the following script is
set mytext "Goodbye moon!"
then magically the text in the label will change to `Goodbye moon!'.