I thought you’d never ask.
Comparative Literature is the study of cultural expressions across languages, periods, genres, and disciplines. Experts in the field acquire familiarity with several languages, frame theories to enable connections among disparate domains, and propose new ways of understanding that arise from considering similarities, differences, and relationships encompassing these diverse objects.
It is important to observe that Comparative Literature is an open project, not a discipline grounded on a single archive or method. It can be defined by contrast with such fields as English, philosophy, literature-in-translation, anthropology, linguistics, etc.— all of which it can include, but none of which circumscribe it. There are examples of Comparative Literature, but no definitive rulebook. We discover what it is by doing it.
For more detail, you might like to look into:
Are We Comparing Yet? On Standards, Justice, and Incomparability. Bielefeld: transcript verlag /Bielefeld University Press, 2019 (Open Access copy available here).
César Dominguez, Haun Saussy and Darío Villanueva. Introducing Comparative Literature: New Trends and Applications. New York: Routledge, 2015. Spanish translation: Lo que Borges enseñó a Cervantes: Introducción a la literatura comparada. Trans. David Mejía. Madrid: Taurus, 2016. Arabic translation: Taqdiym al-adab al-moqarān, itijāhāt wa tatbiyqāt jadīdah. Trans. Fuad Abdel Motteleb. Kuwait: National Council for Arts and Literature, 2017.
Comparative Literature in an Age of Globalization: The 2004 ACLA Report on the State of the Discipline. Baltimore: Johns Hopkins University Press, 2006.
“Comparative Literature?” PMLA 118.2 (2003), 336-341.
“The Dimensionality of World Literature.” Neohelicon 38.2 (2011), 1-7.
“Comparisons, World Literature, and the Common Denominator.” 60-64 in Ali Behdad and Dominic Thomas, eds., A Companion to Comparative Literature. Oxford: Blackwell, 2011.
“Axes of Comparison.” 64-76 in Rita Felski and Susan Stanford Friedman, eds., Comparison: Theories, Approaches, Uses. Baltimore: Johns Hopkins University Press, 2013.
“Cosmopolitanism.” American Comparative Literature State of the Discipline report, 2014, available at http://stateofthediscipline.acla.org/entry/cosmopolitanism.
“By Land or by Sea: Models of World Literature.” 61-69 in Jean Bessière and Gerald Gillespie, eds., Contextualizing World Literature. (New Comparative Poetics, 35.) Brussels: P. I. E. Peter Lang, 2015.
“Poetry — Universal? Progressively So? On World Poetry.” Comparative Literature and World Literature 1:1 (2016), 3-9.
“Trying to Make It Real: An Exchange Between Haun Saussy and David Damrosch.” (Including “Compared to What?” “Comparison — La Petite Phrase de Vinteuil,” and “Conclusion: L’ Inégalité des Dalles.”) Comparative Literature Studies 53 (2016): 660-693.
“Comparative Literature: The Next Ten Years.” 24-29 in Ursula Heise, chief editor, Futures of Comparative Literature. New York: Routledge, 2017.
“The Three Futures of World Literature.” Canadian Review of Comparative Literature / Revue canadienne de littérature comparée 44 (2017): 397-406.
“A Poetics of Global Trolling.” University of Toronto Quarterly 88 (2019): 112-124.
That may not be enough, but it’s the best I can do now.