The syllabus, though certainly underappreciated, is a time-honored genre of expository writing. Its history is long and storied: the earliest known record of one was an object of worship for a prehistoric community in Mesopotamia. The ancient Phoenicians carried syllabi as good-luck-charms on their earliest sea voyages. Hannibal sketched his plans for attacking Rome on the back of a used syllabus, and it was a syllabus that carried to Paris the news of Napoleon's defeat at Waterloo. It has even been speculated that the great Chicago Fire of 1910 was ignited by a burning syllabus.
In recent decades, however, this once-revered genre has been primarily the province of academics, leading--perhaps inevitably--to a preponderance of self-important fluff that skews the genre heavily towards the farcical. Typically those who write them also present them, often in long-winded sessions of reading-recital, to a crowd of students most of whom won't give a shit about it, at least for a few weeks.
Usually a portion of the syllabus comprises a schedule with reading assignments and due dates, though this is by no means universal. Often a professor will offer a tentative list of assigments that will be subject to change, often drastic, over the course of the study period.
Educators often stress the importance of the syllabus to their students by referring to it as a "contract," as in: "this document is my contract with you." Though the practice seems to have fallen out of favor, in years past it was common for the educator to require his students to sign the syllabus, presumably to reinforce its significance as "contract." In this context, the syllabus usually contains grading guidelines that students can expect will be followed, as well as policies regarding missed or late work and participation, so that students might expect fair treatment according to the letter of the contract.
Less formally, though, the syllabus often functions as a "Frequently Asked Questions" sort of document, anticipating the most common and important concerns students might have upon starting the course and answering them up-front. Viewing the syllabus this way casts an even more absurd light upon some educators' habit of reading the document, word-for-word, to his class on the occasion of the first meeting.