When I watch sporn videos on Youtube, the contents of the spot, cyst etc seem to be interchangeably described as 'sebum', 'keratin' and 'pus'.
Now pus I understand - ie infected material from, say, an abscess? But what are the others?
Also - occasionally I have little spots occur overnight - and when I gently squeeze a clear bit of something looking like water (clear and colourless) comes out. So the spot gently pops with minimal pressure and promptly disappears without inflammation.