[dba-SQLServer] File extensions

Sent this hours ago but hasn't appeared, hence trying again  -  so apologies
in advance when the original turns up.

Hello good people on this wet and windy Autumn evening in the UK

Simple question from a simple soul. I keep a weather eye on the SQL server
list but never having actually developed a SQL system my question is: if I
go to look at a client's existing system how can I tell if it is SQL (which
I think it is)? Would file suffixes tell me, or can a developer call a
database anything he/she likes? And if the file suffixes are the answer what
are the magic three letters? Going on from there, if I was offered the
opportunity to take the data away to have a look at it can I just zip up a
file or two, and if so what would I need in order to be able to read the
data in Access when I got back home?

-- Andy Lacey
http://www.minstersystems.co.uk