A database is a collection of data, organized into tables and records. In web design, a web site that writes to a database and/or displays information from a database is referred to as a dynamic web site. Databases are typically used to store information like user account information, product information etc.
A dedicated server is a web server that is used to host one web site only. All the resources on the server is available exclusively to the web site. This is in contrast to shared hosting where the resources are shared by multiple web sites hosted on the server.
Linking to directly to pages within a site, other than the homepage. In the majority of cases deep linking to someone else's domain is acceptable, but there are sites that do not allow deep linking, preferring that all traffic go via the homepage. If unsure, ask permission before deep linking.
Depricated tags, elements or attributes are ones that have become obsolete or they have been replaced by newer versions. Continuing to use a depricated tag/element/attribute might seem to work fine, but it will eventually stop working as newer web browsers stop supporting it.
A declaration at the top of an HTML document specifying the syntax used in the rest of the document. It is possible to publish an HTML document without declaring the DOCTYPE, but doing so could cause serious display problems especially if CSS is used.
The last bit of the domain name, for example ".com", ".net" or ".org". There are hundreds of different domain extensions, including country-specific domain extensions such as ".co.uk" for the UK, ".com.au" for Australia etc.