Cisco calls VLANS 1 - 1005 Normal VLANs. Of those, VLAN 1 is the Cisco default. You can use this VLAN, but your are not allowed to delete it. VLANs 1002 - 1005 are the Cisco defaults for FDDI and Token Ring. These also cannot be deleted.
That leaves us VLANs 2 - 1001 as Normal VLANs that we can add or delete as we wish.
VLANs 2 - 1001 are pruning eligible, while VLANs 1006 - 4094 are not.
When you delete a VLAN, any LAN ports configured as access ports for that VLAN become inactive until you assign them to a new VLAN.