Explanation
A usage report is a comma-separated value (CSV) file that can be used to get a detailed breakdown of resourcesin Oracle Cloud Infrastructure for audit or invoice reconciliation.
The usage report is automatically generated daily, and is stored in an Oracle-owned Object Storage bucket. It contains one row per each Oracle Cloud Infrastructure resource (such as instance, Object Storage bucket, VNIC) per hour along with consumption information, metadata, and tags. Usage reports generally contain 24 hours of usage data, although occasionally a usage report may contain late-arriving data that is older than 24 hours.
Usagereports are retained for one year.

Explanation
When you work with Oracle Cloud Infrastructure, one of the first steps is to set up a virtual cloud network (VCN) for your cloud resources.
VIRTUAL CLOUD NETWORK (VCN) :
A virtual, private network that you set up in Oracle data centers. It closely resembles a traditional network, with firewall rules and specific types of communication gateways that you can choose to use. A VCN resides in a singleOracle Cloud Infrastructure region and covers a single, contiguous IPv4 CIDR block of your choice.
See Allowed VCN Size and Address Ranges. The terms virtual cloud network, VCN, and cloud network are used interchangeably in this documentation. For more information, see VCNs and Subnets.
SUBNETS :
Subdivisions you define in a VCN (for example, 10.0.0.0/24 and 10.0.1.0/24). Subnets contain virtual network interface cards (VNICs), which attach to instances. Each subnet consists of a contiguous range of IP addresses that do not overlap withother subnets in the VCN. You can designate a subnet to exist either in a single availability domainavailability domain or across an entire region (regional subnets are recommended). Subnets act as a unit of configuration within the VCN: All VNICs in a given subnet use the same route table, security lists, and DHCP options (see the definitions that follow). You can designate a subnet as either public or private when you create it. Private means VNICs in the subnet can't have public IP addresses. Public means VNICs in the subnet can have public IP addresses at your discretion. See Access to the Internet.

Managed service that enables you to encrypt your data using keys that you control
* Key Management provides you with
* Centralized key management capabilities
* Highly available, durable, and secure key storage in hardware security modules (HSMs)
* Integration with select Oracle Cloud Infrastructure services
* Uses HSMs that meet Federal Information Processing Standards (FIPS) 140 2 Security Level 3 security certification
* HSM hardware is tamper evident, has physical safeguards for tamper resistance, requires identity based authentication, and deletes keys from the device when it detects tampering
* A HSM is a physical computing device that safeguards digital keys and provides crypto processing Key Management Reference:
https://www.youtube.com/watch?v=N1Tqqg3jUmc&list=PLKCk3OyNwIzuHYigVbdtDOZOfChcotfj2&inde x=9

Explanation
NVMe stands for non-volatile memory express. It is a storage protocol created tofasten the transfer of data between enterprise and client systems and solid-state drives (SSDs) over a computer's high-speed Peripheral Component Interconnect Express bus. The characteristics are:
1) Local NVMe is NVMe SSD-based temporary storage.
2) Itis the locally-attached NVMe devices to the OCI compute instance
3) It is used very high storage performance requirements, lots of throughput, lots of IOPS, local storage and when you don't want to go out on network
4) Oracle does not protect in any waythrough RAID, or snapshots, or backup out of the box and data is not encrypted at rest.