The poem itself tells the inner feelings of a man in love who realises that his aspirations and his outlook on life are much deeper than those of the rest of the people (including his girl-friend). He feels the need to stir those around him, to make them conscious of the seriousness of life and of their frivolity, but at the same time he fears being rejected and mocked at.
There are passages which may be viewed as a criticism of English society of the beginning of the 20th Century.
The poem may be viewed as a embodiment of bathos (a Modernistic style-figure): the lover (Prufrock) wants to be serious but he is just an ordinary (and even comic) individual.
There are several images/expressions in the poem which have become famous, including: