Difference of 余 and 我
As Stan said 余 is archaic and only found in literature. As in

余既为此志。——明· 归有光《项脊轩志》


我 is what modern-day Chinese use as the first-person pronoun.

我喜欢吃苹果。


I asked some Chinese friends and they only recognized 余 as a surname or meaning surplus or extra.