Disaster recovery is deeply embedded into the design of SQL Server, and as such, it’s important to understand and manage your database backup policies carefully. SQL Server databases must be backed up using the built in BACKUP command, either natively within SQL Server or through the use of a SQL-specific third party tool. If no backup has been done on a particular database, it will not be possible to recover in case of corruption, system failure, or accidental deletion of data. Regular filesystem backups are not a substitute for database backups.
Refer to this article for an overview of backup operations in SQL Server. All databases have a configured recovery model, which dictates the kinds of backup and restore operations which are available. In all cases, a full backup should be taken of any database which has never been backed up. In the simple recovery model, regular full backups should be taken on an ongoing basis, while using the full or bulk logged recovery model, regular log and differential backups should be added to the full backup schedule.