The opening sentence to a paper is the thesis statement. It advises readers what will be argued, defended or discussed.
For example, a paper on Genghis Khan might begin with the statement "Genghis Khan was both a product of and ahead of his times." That statement would be followed by the known and supposed facts in Genghis' life which support the statement.
The paper ends with a reaffirmation of the thesis statement with a concluding sentence such as "And so it can be seen that Genghis Khan was a product of his times in his recourse to violence but also ahead of his peers in his respect for the opinions of (some) women and tolerance of other religions."