Surah Falaq and Surah Naas were revealed to alleviate Nabi (Sallallahu Alaihi wasallam) from the effects of Sihr.
We are encouraged in the Ahaadeeth to recite these 2 Surahs daily as a protection for ourselves.
Below is a brief informative leaflet prepared on the Tafseer of Surah Falaq and Surah Naas, by the Uswatulmuslimah organization.