Your question requires several books to answer it! In fact, the poem is so complex in its symbolism that Eliot included his own footnotes to guide the reader. I will address the title of the poem, which refers to the world after WWI. The narrator uses symbols of water and lack of it to show the infertility of our culture, wasted by a lack of love and giving. Eliot's footnote credits Jessie L. Weston's From Ritual to Romance as his source and inspiration for the overarching symbolic structure of the poem. Weston explains that the original Wasteland was part of the legend associated with the Quest of the Holy Grail found in Arthurian legend. Within the Quest for the Holy Grail is an ancient fertility myth having to do with the Fisher King whose death, sickness, or impotence brought about infertility of the land. Note all the images of dryness and death in the opening section: dead land, dull roots, winter, dried tubers, stony rubbish, broken images, dead tree, dry stone, and the repetition of rock are but a few examples. These pertain to the larger "death" of culture brought about and signified by the war.