SAPgui is the application most folks use to interact with SAP. It provides a graphical way to enter vouchers, receipt inventory, process sales orders, etc. It's also the tool generally used to configure and manage SAP.

To get around in SAP, either use the menu or enter a transaction next to the green check. If you know a few transaction codes, entering them is the easiest way to get around in SAP. Generally you'll want to prefix each transaction with "/n"; so if you want to run VA01 (create sales order), just type "/nVA01" and hit enter.

Command Prefixes & Special t-codes

Append to the beginning of each transaction code. When entered without a transaction code, this returns to the main menu.
Append to the beginning of a transaction code to open a new window
End this session (all windows) and ask for confirmation
End this session (all windows) and do not ask for confirmation
Close this window only
Clear the buffer and number ranges
Clear the buffer
(e.g., "/nVA01" will run the "create sales order" transaction. "/n" will return to the main menu)

Command Suffixes

Transactions ending with 1 generally create
Transactions ending with 2 generally change
Transactions ending with 3 generally view
Transactions ending with 4 generally browse
(e.g., VA01 creates a sales order; VA02 changes a sales order, etc)