Muggles' Guide to Harry Potter/Magic/Expulso

Expulso appears to be one of the many spells, like Confringo, that causes things to explode.

We see the Expulso curse being used only once. Shortly after Harry, Ron, and Hermione leave Bill and Fleur's wedding, they stop in an overnight café on the Tottenham Court Road. There, they are attacked by a pair of Death Eaters. One of the Death Eaters uses this spell to blow up the table behind Harry, who is hidden under his Invisibility Cloak, possibly in an attempt to jinx Harry that misses.

While we believe this spell to be a simple explosive, it is uncertain; we have seen in previous battles that curses that miss their target seem to explode when they reach solid objects.