Does Page_Load also execute on an On_Click event?

I thought that Page_Load events executed every time a page was loaded not just the first time. Am I wrong on this?
I have a Page_Load event that writes text to a label to display on the screen:
Output.Text  &=  "Welcome to my Website <br />"  (Output being the ID of a Label control)

I also have an On_Click event for a button to display the same information:
Output.Text  &=  "Welcome to my Website <br />"

After clicking the button, I expected to see the output twice. Once for the page being reloaded and once for the click event. I thought that Page_Load events executed every time a page was loaded not just the first time. Am I wrong on this?

Thanks,
Ken
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