The default pubsub.yaml($HOME/.dapr/components) file is used. And rabbit mq is used for pub sub implementation. Below are the contents of pubsub.yaml file.
The other way to include pubsub.yaml is to create a components directory and create a file called pubsub.yaml and add the below contents to the file. 
And then modify the dapr run command to include components directory path using "--resources-path". 

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: orderpubsub
spec:
  type: pubsub.rabbitmq
  version: v1
  metadata:
  - name: host
    value: "amqp://localhost:5672"
  - name: durable
    value: "false"
  - name: deletedWhenUnused
    value: "false"
  - name: autoAck
    value: "false"
  - name: reconnectWait
    value: "0"
  - name: concurrency
    value: parallel
scopes:
  - orderprocessing
  - checkout


Start a RabbitMQ message broker by entering the following command:
docker run -d -p 5672:5672 -p 15672:15672 --name dtc-rabbitmq rabbitmq:3-management-alpine



Java:

dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --resources-path ../../components mvn spring-boot:run

dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --resources-path ../../components mvn spring-boot:run

Python:

dapr run --app-id orderprocessing --app-port 6001 --dapr-grpc-port 3601 --app-protocol grpc --resources-path ../components  python3 OrderProcessingService.py

dapr run --app-id checkout --app-port 6002 --dapr-grpc-port 3602 --app-protocol grpc --resources-path ../components  python3 CheckoutService.py

GO:

dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --resources-path ../../components go run OrderProcessingService.go

dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --resources-path ../../components go run CheckoutService.go

CSharp:

dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --app-ssl --resources-path ../../components dotnet run

dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --app-ssl --resources-path ../../components dotnet run

Javascript:

dapr run --app-id orderprocessing --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --resources-path ../../components npm start

dapr run --app-id checkout --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --resources-path ../../components npm start