What is the meaning of the parameters?

Database parameters
name	default	description
database_driver	pdo_sqlite	Should be pdo_sqlite or pdo_mysql or pdo_pgsql
database_host	127.0.0.1	host of your database (usually localhost or 127.0.0.1)
database_port	~	port of your database (you can leave `~` to use the default one)
database_name	symfony	name of your database
database_user	root	user that can write to this database
database_password	~	password of that user
database_path	`"%kernel.root_dir%/../data/db/wallabag.sqlite"`	only for SQLite, define where to put the database file. Leave it empty for other database
database_table_prefix	wallabag	all wallabag's tables will be prefixed with that string. You can include a `_` for clarity
database_socket	null	If your database is using a socket instead of tcp, put the path of the socket (other connection parameters will then be ignored)
database_charset	utf8mb4	For PostgreSQL & SQLite you should use utf8, for MySQL use utf8mb4 which handle emoji

Configuration to send emails from wallabag
name	default	description
mailer_transport	smtp	The exact transport method to use to deliver emails. Valid values are: smtp, gmail, mail, sendmail, null (which will disable the mailer)
mailer_host	127.0.0.1	The host to connect to when using smtp as the transport.
mailer_user	~	The username when using smtp as the transport.
mailer_password	~	The password when using smtp as the transport.

Other wallabag's option
name	default	description
locale	en	Default language of your wallabag instance (like en, fr, es, etc.)
secret	ovmpmAWXRCabNlMgzlzFXDYmCFfzGv	This is a string that should be unique to your application and it's commonly used to add more entropy to security related operations.
twofactor_auth	true	true to enable Two factor authentication
twofactor_sender	no-reply@wallabag.org	email of the email sender to receive the two factor code
fosuser_registration	true	true to enable public registration
fosuser_confirmation	true	true to send a confirmation by email for each registration
from_email	no-reply@wallabag.org	email address used in From: field in each email
rss_limit	50	limit for RSS feeds

Redis configuration
name	default	description
redis_scheme	tcp	Specifies the protocol used to communicate with an instance of Redis. Valid values are: tcp, unix, http
redis_host	localhost	IP or hostname of the target server (ignored for unix scheme)
redis_port	6379	TCP/IP port of the target server (ignored for unix scheme)
redis_path	null	Path of the UNIX domain socket file used when connecting to Redis using UNIX domain sockets