Tony explained what SQL is as well as I could have. I've used SQL in a few database classes but I'm still not an expert at it, I just know the basics. (In the database class I'm taking this semester, we had to write the code to create our own [simulated] databases, rather than just querying an existing database!)
Most of the time you'll use SQL to query (search) and update a database, although you can use to create whole databases and do all sorts of fun stuff like that. If you are already a little familiar with databases (like if you've ever used Microsoft Access) that will help, but if you understand what fields, records, tables, and data types are you should be fine. Depending on how in-depth SQL code you will be writing, you may need to understand the basics of relational databases (like what keys and foreign keys are) since that's what most databases are. There's a lot of SQL tutorials available online and lots of books you can buy; here are a few tutorials I found from a Google search (keep in mind there are subtle differences in SQL depending on what database you are using, like if you're using MS Access, Oracle, or IBM DB2):
http://www.sqlcourse.com/ (This looks like a good one, you can even run your own SQL code and see what happens!)
http://www.w3schools.com/sql/default.asp
http://www.1keydata.com/sql/sql.html (Contains a list of common commands in the blue side bar)
Also it's possible that not everyone there knew SQL unless they are all CS (Computer Science) majors or something. One thing I've noticed (that is especially common among freshman CS majors) is that CS people don't like to admit how much they don't know; they'd rather rattle on about what little they do know in an attempt to make themselves look smarter
My first semester as a CS major, I was really nervous because I'd never programmed before and all the guys in the class kept talking about computer stuff that I didn't know about, but when I started getting the high scores on the tests I learned that they were just all talk! lol
Good luck with your research!
