Yes, a foundation is the bit at the bottom of the building, often under the ground and it's the bit that you build, or lay, first and then everything else is built on top of it.
是的,「foundation」在這裡指的是建築物的基礎,通常位於建築物底部,常常埋在地下,是最先建造或鋪設的部分,之後所有的結構都建築在它之上。