What means the SAP transaction codes?

Naming convention for tcodes in SAP is dependent on the area of application and it's functionality which is represented by first two characters. Last two characters are generally are numerals which are logically assigned sequence numbers. For example: Eng = German Sales = Vertrieb Order = Auftrag .....VA01 - Sales Order Create, VA02 - Sales Order Change, VA03 - Sales Order Display Delivery = Lieferung....VL01N - Sales Delivery Create New, VL02N Sales Delivery Change New, VL03N - Sales Delivery Display New (N in the end generally means NEW, in such case there would be an old transaction without N as well) Invoice = Faktur ....VF01 - Sales Invoice Create, VF02 - Sales Invoice Change, VF03 - Sales Invoice Display Generelly numerals 1, 2 & 3 in the end represent Create, Change & Display respectively. Similarly procurment in German is Erwerbung, hence the tcode ME21/ME22/ME23 - Purchase Order create/change/display where 'M' stands for Materials 'E' stands for Erwerbung in German. All the transactions follow the same naming convention.