When the bride and the groom are at the front of the church they can face the congregation or the altar.

Facing the altar, with their backs to the congregation, I would stand between them and the altar. Facing the congregation, the couple would stand in approximately the same spot, but face the congregation with me between them and the congregation and my back would be to the congregation.

Neither choice is "right" or "wrong". It is often just a matter of your comfort zone.