The ArcGIS APIs for Silverlight, Flex, and JavaScript allow you to develop web GIS applications using a framework familiar to you. Each API offers the same suite of common GIS functionality, including the ability to edit features and attributes over the web.
The APIs are designed to be accessible to beginning programmers. Each API has a full online help site with "Getting Started" docs, working samples, and a detailed component reference.
If you need to go beyond the capabilies of the APIs or expose custom business logic, you can use server object extensions to access ArcObjects, the deep suite of components on which ArcGIS products are built. For intermediate to advanced developers, server object extensions unlock the full power of ArcGIS for your web apps.