This attack was taught to Goku by King Kai, during his time in the afterlife. It allows the user to borrow energy from all the things in the universe. The energy is gathered by the user raising their arms upwards, this however does leave them open to attack as the strength of the attack is proportional to the time it takes to charge.

Goku forming a Spirit Bomb

GokuSuperGenkiDama super spirit bomb

Goku's Super Spirit Bomb