Country Music is comprised of several "types" of music. There is classic country, contemporary country, bluegrass, alt-country, and western swing. When introducing country music to a friend, you might want to start with contemporary country, as it has more leanings to pop, and is sometimes also called "country pop."
Classic Country
Typically "classic" country is music recorded prior to 1985 or thereabouts. Classic country is also sometimes called "traditional" country. While several artists post 1985 are traditional, the majority swing towards "country pop."

Top 10 Classic Country Males
Top 10 Classic Country Females
Top 10 Classic Country Duos/Groups
Contemporary Country
"Contemporary," country is is music recorded post 1985. Much of it leans towards "country pop" which are CDs with songs that have crossed over to have success on the "pop" charts.

Top 10 Contemporary Country Males
Top 10 Contemporary Country Females
Top 10 Contemporary Country Duos/Groups
Bluegrass
Bluegrass has been around the longest, and while you might think of Bluegrass musically as instrumental, there are lyrical pieces as well.

Top 10 Bluegrass CDs
Alt-Country
The alt-country class is probably the most difficult to explain. Much of it could also be considered "Texas Country," and many of the alt-country artists have big followings in Texas.

Top 10 Alt-Country CDs
Western Swing
Western Swing is music that is most commonly referred to as the style of Bob Wills.

Top 5 Western Swing CDs