Sevillanas are a set of four individual dances: Primera, Segunda, Tercera and Cuarta sevillanas. These sets are strictly codified, so once you have learned the steps, you can dance sevillanas anywhere and only encounter minor variations (especially in the third and fourth sevillanas). While most flamenco enthusiasts insist that sevillanas are not flamenco, the dances are still taught to beginning flamenco students to help prepare them for the more difficult freestyle forms of flamenco.
Each of the four sevillanas consists of three verses, or coplas. The first copla always starts with an entrada using the paso de sevillana -- the basic sevillana step -- followed by a verse step that is different for every copla. The second and third coplas start with a connector step that usually consists of one pasada and one paso de sevillana, followed by a verse step. The final copla ends with a cierre, or closing step. The basic structure of a sevillana is entrada and first copla step, followed by the connector and second copla step, followed by another connector and the third copla step, and ending with the cierre. See the Resource below for a detailed chart of the individual steps for each dance.
The individual steps of the coplas incorporate moves seen in flamenco (like the golpé) as well as moves seen in more mainstream forms of dance (like ballet's pas de bouree). The footwork and armwork of the copla steps can be rather complicated to break down, which is why it is easiest to learn the dances in sections with an instructor. Children in Spain start learning the dances at an early age, but in the United States, your best bet is to find a qualified flamenco instructor.
Sevillanas are danced face-to-face with a partner to sevillana music, which is in three-quarter time. For public performance women often wear traje gitanos; the dramatic turns and passes of sevillanas are emphasized by the colorful ruffled dresses. Unlike many folk dances, armwork in sevillanas is just as important and can be just as complicated as footwork. Despite this, you shouldn't worry too much if you jump into a sevillana only to stumble through it. As with other folk dances, sevillanas are supposed to be fun. Getting to where you're supposed to be is more important than how you get there.