.env files allow you to put your environment variables inside a file. It is a simple text file with each environment variable listed one per line, in the format of KEY=VALUE. Lines starting with # are ignored. For example:
# settings and private keys
DATABASE_PASSWORD=someval
REDIS_ADDRESS=localhost:6379
API_KEY=fb6b05d6e75a93e30e22334443379292ccd29f5d815ad93a86ee23e749227
SECRET_KEY='helloworld'