How would you define the term “reformed theology” to someone who attends church, but maybe does not possess a great deal of knowledge concerning church history or the nuances of Christian theology?
Well, there’s nothing magical about the word “reformed,” and I think there’s a lot of misunderstanding about it. It’s closely related to the Reformation, of course, and, in the Reformation, there was a recovery of the Holy Scriptures. There was a return to the theology of the early church and the Bible, particularly as related to God’s grace and salvation by faith alone in Christ alone, on the basis of the Scriptures alone. Those were some of the distinctives of Luther and Calvin and Cramner – a whole array of Reformers in the 16th century. So when we talk about “reformed theology,” we’re really talking about Biblical theology – Biblical theology that has been refracted through or seen in the prism of the great debates of the 16th century, hence the word “reformed.” There’s nothing magical about that word and we don’t mean to say anything other than sound Biblical teaching related to God and His grace and salvation through faith in Jesus Christ, His Son. That’s really what we mean by it.
Source: Reformed Theology and the Church: An Interview With Dr. Timothy George
The interview is, for obvious reasons, mostly focused on Calvinism and Reformed Theology within the SBC, but his views are relevant and thought-provoking even if you are not Southern Baptist.
What Does the Text Say? 
Excellent answer from Dr. George. Too many people use “reformed theology” as a way to shave certain people away, until all that is left is a homogenous group of people (i.e. to be Reformed in theology requires infant baptism, requires one to be amillenial, etc.)