A Scottish country dance (SCD) is a form of social dance involving groups of mixed couples of dancers tracing progressive patterns according to a predetermined choreography. Country dancing is often considered a type of folk dancing although this is not strictly true because it also has its roots in the courtly dances of the Renaissance.
When it first became popular around the 18th century, it filled the niche that is occupied today by ballroom dances such as the waltz or tango, as a fairly refined form of entertainment. Related dance forms include English country dancing and contra dancing. The connection to styles like ceilidh dancing, "Old Time" dancing, Irish set dancing, or square dance is more tenuous.
Also, Scottish country dancing should not be confused with Scottish highland dance, which (today) is closer to a sport rather than a social pastime, mainly being danced in competition and displays. There is a certain amount of cross-over in that there are Scottish country dances that include highland elements as well as highland-style performance dances which use formations otherwise seen in country dances, but other than that the styles do not really have a lot in common today.
Addendum/Rant by kswingruber: As creator of this microbadge, I feel compelled to comment about the video clip in this "explanation"... Bowah ha ha ha! That is NOT a video of Scottish Country Dancing, but rather Scottish Highland Dancing. The text above even says "Scottish country dancing should not be confused with Scottish highland dance". Yeah sure, the little microbadge LOOKS like highland dancing, but that position is also used in some country dances...