A web application backup will include the IIS settings (that exist inside Office SharePoint Server) and all content databases that are associated with the web application. This is a more granular backup than the entire farm, but is recommended in addition to regular backups at the farm level. Web application backups can be performed through the Central Administration GUI, Windows PowerShell, and using STSADM. Note that if you are performing this backup for the first time, you must perform a Full backup before you can perform Differential one.
To back up a web application by using the Central Administration website, perform the following procedure: