Page 133 - Basic Japanese

You will notice that the mood we call the polite imperfect
ends in -masu for all the verbs (-su for the copula); the polite

perfect ends in -mashita for all the verbs (-shita for the copula);
and the polite tentative ends in -mashō for all the verbs (-shō for
the copula). The verb forms that appear before these polite

endings are called infinitives (or pre-masu forms), and they all
end in the vowel -e or -i. See 4.3 and 4.8 for more about

infinitives. The plain gerund ends in -te or -de (no ending for the
copula), and there are certain changes in the verb stem itself.