SharePoint development relies on “12-hive” folder and each who writes code for SharePoint uses that folder intensively. SharePoint uses that folder to store features, log, content types are other stuff.

12 hive folder structure is not private and your can find full description all folders in google, the core folders you should know about are the following:

• \ADMISAPI - The directory contain the web service used used by the SharePoint Central Administration and appears as a virtual directory.
• \BIN - The directory contains all the core binary files, utilities that are used by Windows SharePoint Services. Your command line tools such as STSADM.EXE reside in this folder
• \BIN\LCIDD - A directory will be created for each language will be created that contains language specific binary files.
• \CONFIG - This directory contains a set of configuration, binary and resource files used by SharePoint. Some files are the default values which will be copied to web site instances.
• \DATA - SharePoint uses this directory structure for the indexing services where content will be indexed.
• \HCCab\LCID - This directory has a set of cab files containing manifest and content information used by the SharePoint help system
• \HELP - The folder contains a compiled html help file (.chm) used by the configuration wizard.
• \ISAPI - This directory contains all the standard Web Services for SharePoint and some additional DLL’s, resources and configuration files that the web services use. Every web application provisioned in SharePoint will have a virtual directory strong>/_vti/_bin that points to this directory, thus giving each web application it’s own set of web services.
• \ISAPI\HELP - This directory contains all the help files used by SharePoint. The folder also contains LCID sub directories for each language installed, thus globalizing the help system.
• \LOGS - This is the directory that you will visiting frequently whilst doing development and administration as it contains the log files of what SharePoint did and what errors occurred.
• \RESOURCES - This directory contains the core.resx file used for creating language packs for SharePoint. If you are going to be localizing your SharePoint sites with different languages and cultures, this is the folder to do it in.
• \TEMPLATE - This directory structure contains the core web site functionality in SharePoint, that is the features, templates, configurations, resources of a web site. What is important to note about this directory structure is that the Virtual Path Provider hides and masks this directory structure, thus it appears under each web site, list in a completely different structure.

Source

---

SharePoint provides you two models for development – Web Services and API for object model. But very often developers are a bit confused about what to use and when.

SharePoint API provides access to all pillars of SharePoint – advanced functionality via features set and good performance . It’s a preferable solution when code resides on the SharePoint server with the access to server to deploy features and other’s library.

SharePoint Web Services provide almost the same level functionality to manage SharePoint. There is a small performance challenged due to object’s serialization/de-serialization and network latency, comparing to API. But the principal only difference with API in the context of usage. Web Services are applicable to remote SharePoint instances, when you have limited access, or don’t have any access to deploy your features and libraries. The only way to manipulate with SharePoint data in this case is via standard Web Services, which can be found in the following MSDN article.

There is a tend that Microsoft moves their services online and we have Microsoft Online Services which demonstrate how SharePoint, Exchange and other servers works in SaaS model. In this case managing online SharePoint services is available only via Web Services.

---