The main components are:

1. AWSTemplateFormatVersion (Optional): Specifies the template format version
2. Description (Optional): Human-readable description of the template
3. Parameters (Optional): Input values for the template
4. Mappings (Optional): Static lookup tables
5. Conditions (Optional): Controls resource creation based on conditions
6. Resources (Required): AWS resources to create
7. Outputs (Optional): Values returned when viewing stack properties

AWSTemplateFormatVersion: '2010-09-09'
Description: 'Simple web server template'
Parameters:
  InstanceType:
    Type: String
    Default: t2.micro
Resources:
  WebServer:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: !Ref InstanceType
      ImageId: ami-0abcdef1234567890
Outputs:
  InstanceId:
    Value: !Ref WebServer