I am pretty new to application development/protocols, but what are some of the most common protocols used when sending data to/from an application/database server. i.e. if I login to a system (for arguments sake a payroll system), and enter some details, read some data etc, what are the more common protocols apps use for passing this data from its db/app infrastructure to my client front end, be that a browser for web based apps or thick client software for other types of app? Are there some common protocols dependant on the type of application used? Excuse my ignorance.