subdivision problem glitch When I'm adding subdivision modifier my object freaks out. I'm new to blender and don understand why :o if somebody knows why, it would be greatly appreciated.

here is with subdiv modifier


here is without
In the picture below, you can see the effect of extra edges placed where you need a surface to keep its shape, that is, have sharper corners or edges.
The bottom row has a smoothing modifier on it.  So you have to cut more edges (or use Loop Cut as edna said), where you need an edge or corner to be sharper.