The "te" form of the Japanese verb "iku," or to go. Iku is a ru verb, so in order to conjugate it to its te form, you must take the
base (which would be "i," in this
case), and add a "tte" (って) onto it. Typically verbs that end with a "ku" sound get an ite (いて) added onto the
base, but iku is the only exception to this rule.
With kanji, it's written as "行って".