DESCRIPTOR_POOL_CREATE_FREE_DESCRIPTOR_SET_BIT specifies that descriptor sets can return their individual allocations to the pool, i.e. all of allocateDescriptorSets, freeDescriptorSets, and resetDescriptorPool are allowed. Otherwise, descriptor sets allocated from the pool must not be individually freed back to the pool, i.e. only allocateDescriptorSets and resetDescriptorPool are allowed.

DESCRIPTOR_POOL_CREATE_HOST_ONLY_BIT_VALVE specifies that this descriptor pool and the descriptor sets allocated from it reside entirely in host memory and cannot be bound. Descriptor sets allocated from this pool are partially exempt from the external synchronization requirement in updateDescriptorSetWithTemplateKHR and updateDescriptorSets. Descriptor sets and their descriptors can be updated concurrently in different threads, though the same descriptor must not be updated concurrently by two threads.

DESCRIPTOR_POOL_CREATE_UPDATE_AFTER_BIND_BIT specifies that descriptor sets allocated from this pool can include bindings with the DESCRIPTOR_BINDING_UPDATE_AFTER_BIND_BIT bit set. It is valid to allocate descriptor sets that have bindings that do not set the DESCRIPTOR_BINDING_UPDATE_AFTER_BIND_BIT bit from a pool that has DESCRIPTOR_POOL_CREATE_UPDATE_AFTER_BIND_BIT set.