Tawassul in Arabic means communicating, specifically as a genuine or humble request.

In Dua al-Tawassul, God is prayed and pleaded to by swearing upon the position of the 14 Maʿṣūmin (infallibles). 

Although not taught by any of the Infallibles, the content of this supplication does not go against the Quran nor the accepted position of the ahadith.

Although there is no specific day or time to recite this supplication, most believers recite it on Tuesday night.