1) backup and restore ESXi host configuration
2) Backup all together, ESXi config and VMs, we cannot do that. We got to take VMs backup separately. there's many backup solutions available. One of them is vSphere Data Protection (VDP), please refer following tech paper for the same. It's for VDP 5.1, but I am sure you will be able to locate similar documentation for latest version too which is VDP 6.0
http://www.vmware.com/files/pdf/techpaper/Introduction-to-Data-Protection.pdf
Since your question is associated with vSphere 4.1, I would recommend using following documentation for detailed info. about it.
http://www.vmware.com/pdf/vsphere4/r40/vsp_vcb_15_u1_admin_guide.pdf