I'm trying to build a sample docker image. When I run the following command:

docker build -t sample .

Where does the docker image go?

Here is my Dockerfile:

FROM node:boron

# Create app directory
RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

# Install app dependencies
COPY package.json /usr/src/app/
RUN npm install

# Bundle app source
COPY . /usr/src/app

EXPOSE 8080
CMD [ "npm", "start" ]