title: List comprehension example I don't understand
body: <p>I'm having trouble understanding a particular list comprehension example. In the sample code below a list comprehension is used for the parameter of the set method. Most examples I've seen usually look like this "x for x in y". I've read documentation but it isn't clearing it up for me. What exactly is [marks for name] doing. Shouldn't it be [marks for marks]?</p>
  
  <pre><code>marksheet = []
  for _ in range(0,int(input())):
      marksheet.append([input(), float(input())])
  
  second_highest = sorted(list(set([marks for name, marks in marksheet])))[1]
  print('\n'.join([a for a,b in sorted(marksheet) if b == second_highest]))
  </code></pre>