We used to live in a house that was on a concrete foundation. Before we moved out it came a huge rain and there was about 2 inches of water in one part of the wall and lowered down to the carpet level across the room. My step-dad said it was the foundation. And I wanted to know what that may have possible been. Or what else could it be? There also want very good drainage around the house when it rained. Please help. Open to any suggestions!

Poor drainage outside the foundation would do it every time, water exerts impressive pressure. It will find its way through any gap or porous surface in its way... and concrete is somewhat porous.

It apparently has insufficient waterproofing as well as improper drainage for the given soil conditions.

As smoothy suggested or it could be simply clogged, too small, or misdirected downspouts.
Do you have a sump pump? Are there stains to suggest it has happened before?
Was it clear water and not a possibility of sewer backup?