They both mean I。 But I still can't understand the real difference. Also, I want an example sentence. When I use Google Translate and Bing Translator, the result is same.
我 is also used in ancient times. For example, in 戰國策 之 鄒忌諷齊王納諫
Practically, 余 is no long in use unless in poems or classic literature.
It would be more interesting to look at the various characters refer to 'I'.
我 is certainly the most widely used one.
咱 is colloquial.
俺 is more colloquial and vulgar.
阿拉 is commonly used in Shanghainese dialect.
吾 is in Cantonese dialect.
– and the list goes on.
Recent researches show that there are differences in grammatical forms of the 2 characters in ancient scripts before or in Qin Dynasty (appr. before 207 B.C.), but in later classical Chinese litterature, they are synonyms.
In today's language, 余 as a pronoun has died and only can be seen when people try to write in classical Chinese.