In Pennsylvania, 6,165,478 people voted in the election. Trump
received 48.18% of the vote and Clinton recieved 47.46%. This
doesn't add up to 100% because other candidates received votes. All
together these other candidates received 100% - 48.18% - 47.46% =
4.36% of the vote.
Suppose we could select one person at random from the 6+ million
voters in PA (note: PA is the common abbreviation for
Pennsylvania). We are interested in the chance that we'd choose a
Trump, Clinton,...