word, e.g. “arguing”
stemmed word, e.g. “argu” (note, that “argu” is not a word, it is just a stemmed (normalized) version of “arguing”, “argued”, etc.)
The Porter stemming algorithm is a process for removing the commoner morphological and inflexional endings from words in English. Its main use is as part of a term normalisation process that is usually done when setting up Information Retrieval systems.