Wilco is an abbreviation for 'will comply' used in two-way radio communications. It signals that the receiving station has heard the transmission, understood the directive, and intends to execute the requested action. It inherently includes the meaning of 'roger', making the phrase 'roger wilco' redundant.
Heard on the job
Tower, this is flight two-niner, descending to three thousand feet, wilco.
Insider tip
Never say 'roger wilco.' Since wilco means 'I have received your message and will comply,' adding roger is redundant and marks the speaker as an amateur.