Syntax in computer terms: Refers to the spelling and grammar of a programming language. Computers are inflexible machines that understand what you type only if you type it in the exact form that the computer expects. The expected form is called the syntax.
A complete syntax would be an entire syntax command, such as "ipconfig /all" from command prompt. OR any other complete command with switch(s) http://en.citizendium.org/wiki/Syntax_(computer_science)
As far a 'Google search interface ', that is the frontend of the search engine, what it looks like to the end user, the 'interface' where you type the search string or click on links, presented by google. http://en.wikipedia.org/wiki/Interface
