Difference between Classic Authentication and Claim based authentication

What are the differences between Classic Mode Authentication and Claims based Authentication?

Classic Mode Authentication: It refers to the integrated windows authentication. You cannot configure the Forms based authentication if your web application is using Classic Mode Authentication. You can convert a web application from Classic Mode Authentication to Claims Based Authentication. However, that can only be done using PowerShell commands and its an irreversible process. I have detailed steps to convert the web application from Classic Mode authentication to Claims Based Authentication.

Claims Based Authentication: SharePoint 2010 is built on Windows Identity Foundation. It enables authentication from windows as well as non-windows based systems. This also provides the capability to have multiple authentication in a single URL.

What is Server Farm and Front End Web Server

Server Farm:
SharePoint Server farm environments can encompass a wide range of topologies, and can include many servers or as few as two servers.

• A small server farm typically consists of a database server running Microsoft SQL Server , and one or more servers running Internet Information Services (IIS) and Office SharePoint Server 2007. In this configuration, the front-end servers are configured as Web servers and application servers. The Web server role provides Web content to clients. The application server role provides Office SharePoint Server 2007 services such as servicing search queries, and crawling and indexing content.
• A medium server farm typically consists of a database server, an application server running Office SharePoint Server 2007, and one or two front-end Web servers running Office SharePoint Server 2007 and IIS. In this configuration, the application server provides indexing services and Excel Calculation Services, and the front-end Web servers service search queries and provide Web content.
• A large server farm typically consists of two or more clustered database servers, several load-balanced front-end Web servers running Office SharePoint Server 2007, and two or more application servers running Office SharePoint Server 2007. In this configuration, each of the application servers provides specific Office SharePoint Server 2007 services such as indexing or Excel Calculation Services, and the front-end servers provide Web content.
• You can deploy Office SharePoint Server 2007 in a server farm environment if you are hosting a large number of sites, if you want the best possible performance, or if you want the scalability of a multi-tier topology. A server farm consists of one or more servers dedicated to running the Office SharePoint Server 2007 application

Front End Web Server

            In a server farm environment, the front-end Web servers contain only the files and settings required to route requests from clients to the appropriate sites in the database. Unlike in SharePoint Team Services v1.0 from Microsoft, they do not contain site data.
            All site content and all configuration data is shared for all front-end Web servers in a server farm. To get the best performance and the best protection against hardware failure, you should configure Windows SharePoint Services identically on all the front-end Web servers in your server farm.

Site collection & Subsite defintion

Site Collection:
                 A SharePoint site collection is a hierarchical set of sites that can be managed together. Sites within a site collection have common features, such as shared permissions, galleries for templates, content types, and Web Parts, and they often share a common navigation. A site collection contains a single top-level site, and any number of subsites organized in a hierarchy. A subsite is a single SharePoint site within a site collection.


SubSites:
A subsite can inherit permissions and navigation structure from its parent site, or these can be specified and managed independently. Creation of subsites can be delegated to users of a site collection, but creation of site collections must be performed by a service administrator.