CPU limits and capacity

I read the docs, and I want to make sure I understand it. When I assign a single socket/single core to a vm, does that mean proxmox will reserve a whole core to just that vm, or does it mean that that vm can only use 1 core max and no more? I am trying to size my host for the preposed work loads. So is I have 10 cores available and 30 vms are all given 1 core, that they will all share the 10 cores?

Brad