Sales and Distribution
SD模块是SAP最早开发出来的模块，最初主要是为了一家药厂开发的。经过不断的改善，现在SAP SD模块已经发展得比较完善了。SD模块中主要控制如下的一些程序：
Sales inquiry, sales quotation, sales contract, sales order entry; delivery creation and processing; transportation planning; shipping; billing. 还有一些控制组件，如：pricing procedure, text determination procedure, route determination, partner determination, shipping point determination, revenue account determination. There are several unusual components also included in SD module: export, scheduling agreement, etc.
Material Management
MM module is also a very important part of the SAP R/3 system. Its main functions includes: purchasing, inventory management, warehouse management. In purchasing, many functionalities are provided: vendor selection and evaluation, purchasing requisition and purchase order release, sourcing plan, etc. In inventory management, First In First Out, First In Late Out and other inventory concepts are provided in the system. IN warehouse management, manay plants from different companies can be managed under one warehouse numbers, it controls the materials at the level of storage bin (the smallest unit in inventory).
Production Planning
PP module control the shop floor planning. R/3 system provides over twenty different production planning methods. Production order against independent requirement or sales orders requirement. Different MRP run type, etc.
FI/CO
FI/CO module provide functions in financial transaction and controlling. General Ledger account, Account receivable, Account payables, Cost center, financial posting from sales and distribution module.
HR
Human resource is developed in recently years. It contains personnel administration and personnel development.
ABAP
ABAP programm is for SAP. It look like C++ language. It is used to cusotmize different report or do some configuration in the system.
SAP中有几个比较显著的概念，这些概念贯穿于SAP R/3系统当中，并不随模块的变化而有不同。我在这里将我的粗浅的意见写出，与各位高手交流。
1、Item Category.
在SAP 中ITEM CATEGORY 是一个非常重要的东西。它不但在SALES中起作用，也在其它的各个订单实施阶段起重要作用。同一个ITEM，它在不同的情况下，可能具有不同的ITEM CATEGORY，这样东西控制了定价方式，ITEM是否RELATED TO delivery, 是否related to billing, 是否是免费货物，等等。
2、Condition technique.
这是在SAP中广泛应用的一种技术，它被用来决定不同的TEXT文本，不同的价格在不同的销售区域中，自动地决定SAP中被称为伙伴的Business parties. 其说到底，就是几张相互关联的表格。它一般包括五个方面：Condition table, Access sequence, condition type, condition precedure, condition record. Condition table 又被称为KEY，不同的KEY就是用来组成Condition technique的最基本的部分。Access sequence是指系统依据怎样的顺序来寻找符合要求的condition record. Condition type是指各种不同的condition, 包括不同的calculation type 和calculation basis. Condition procedure是一种程序，它包含了一个或多个condition type. 它是与document type or other thing 相连。Condition record则是在FUNCTIONAL方面来输入的。它包含系统最后找到符合一系列条件的数值。Condition technique在4.0中有了更显著的增强。
3、Batch management and Classification
BATCH是用来对不同批次的物料进行管理。它既出现于SALE模块中，用于选择不同批次的产品，又出现在库存管理中，用于到期管理。它通过定义众多的特征，将具有某类特征的产品唯一的定义为一个批次。批号可以由系统自动产生，也可以由人工输入。BATCH有三种定义的层次：一是整个CLIENT LEVEL， 二是PLANT LEVEL， 三是Material level. 这种定义是非常重要的，必须在还没有开始之前就定下来了，要是你已经开始使用BATCH然后再想改变的话，就要Reorganize整个BATCH system了
