Elastic Load Balancing (ELB) is an AWS service that automatically distributes incoming application traffic across multiple Amazon EC2 instances to balance the workload. This helps ensure high availability and fault tolerance by distributing the traffic to healthy instances and routing it away from failed instances, improving overall performance. ELB provides health checks on instances and scales automatically based on incoming traffic. With integration of AWS Auto Scaling, desired count of instances can be maintained to handle the incoming traffic.

Amazon EC2 provides a variety of instance types, optimized for different use cases. Instance types are grouped into families based on their general characteristics, such as memory, CPU, storage, network capacity, GPUs, and more. This enables customers to choose the best instance type for their workloads, considering factors like performance, cost, and resource requirements. Examples of instance type families include T2, M5, C5, R5, I3, G4, and P3.

An Amazon Machine Image (AMI) is a template that contains software configurations, including an operating system, applications, and other settings. It is used to launch and set up an Amazon EC2 instance quickly and easily. Users can choose from a wide range of predefined Amazon, community-driven or their custom AMIs, allowing them to create EC2 instances with the desired software and configurations already in place.

Amazon Elastic Block Store (EBS) is a storage service designed specifically for Amazon EC2 instances, providing highly available, consistent, and low-latency block storage volumes. EBS volumes are automatically replicated within the same Availability Zone to protect against component failure, providing fault tolerance and high durability. They can also be created from snapshots, allowing users to easily backup their data and migrate volumes across instances or regions.

Auto Scaling is a service that allows you to automatically adjust the number of Amazon EC2 instances in your environment based on predefined scaling policies, health status, and workload demand. With Auto Scaling, you can ensure that your application maintains optimal performance while efficiently managing costs. Auto Scaling can automatically launch or terminate instances, add instances to or remove instances from load balancing, and provide instance health monitoring to maintain your desired instance count.

Amazon EC2 Spot Instances are unused EC2 instances whose capacity is available for purchase at a significantly lower price compared to On-Demand instances. Spot Instances can be used for fault-tolerant, flexible workloads or applications with significant cost savings. However, they can be interrupted and reclaimed by AWS with a two-minute notice when AWS requires the capacity back, so they are best suited for workloads that can handle occasional interruptions.

Instance Metadata is data about an EC2 instance, such as instance type, instance ID, and more. User Data is custom data or scripts provided by the user during instance launch. Both Metadata and User Data can be used to configure and manage instances, including passing information between instances and triggering automation tasks. These can be accessed and used by applications running on the instance to make dynamic decisions or configure software at boot time.

A security group is a virtual firewall that controls the traffic for one or more Amazon EC2 instances. You can create security groups based on your requirements and then assign them to your instances, allowing or denying traffic based on rules. Rules can be configured for both inbound and outbound traffic, by specifying source or destination, protocol, and port range. Security groups help protect your instances by isolating them from unwanted traffic and ensuring only authorized access.

An Elastic IP address is a static, public IPv4 address that you can allocate to your AWS account and associate with an Amazon EC2 instance. Elastic IP addresses enable you to mask instance failures by remapping the address to another instance in your account. Unlike a regular public IP address, which changes when you stop and start your instance, an Elastic IP address remains associated with your account until explicitly released and is ideal for use cases that require fixed IP addresses for reliability or integration with third-party services.

Placement Groups are logical groupings of instances within a single Availability Zone, enabling you to influence their placement and get the desired performance characteristics. There are three types of placement groups: Cluster, which packs instances close together for low-latency and high network throughput; Partition, which spreads instances across logical partitions within the same zone, providing fault tolerance for more independent workloads; and Spread, which ensures instances are placed on distinct underlying hardware, increasing fault tolerance for a small number of critical instances.