It is likely that the guitar evolved from predecessor stringed instruments of what we now call Greece, Turkey, Azerbaijan, Syria, Iran and Iraq. The earliest western stringed instrument that resembles a guitar may be the Azerbaijani kopuz, which later became the Turkish saz, possibly through or along side an Assyrian ancestor instrument. Researchers have attempted to trace the guitar from the ancient Greek lyre and the "Asiatic" kithara, through the Arabic oud, the European lute and theorbo, then on to the vihuela and finally the modern nylon stringed guitar, but there is little agreement as to the exact origin. In any case, I venture to assume that each of these predecessor instruments had relevant playing techniques, some of which may continue in the repertoire of modern day guitarists.
The guitar, as it is played in flamenco, largely began as an accompaniment instrument to voice and to dance. It was in the 1930s that Ramón Montoya adapted several guitar techniques from the classical tradition for flamenco, which expanded the early flamenco style of guitar playing. Prior to the 1930s, most guitarists used substantially less ornate techniques that, while strong and rhythmic, may not have been as varied harmonically or melodically as we find now. The two most defining techniques that differentiate flamenco guitar from classical are 1) rasgueado, and 2) alzapúa. Rasgueado consists of many patterns in which the fingers of the strumming hand flick up and down across the strings, creating a variety of textures. Alzapúa is a technique in which the thumb of the strumming and plucking hand is pushed through one or two strings in an up and down motion and can create a powerful melodic phrase.
Over time, guitarists have developed the rhythmic capacity to mimic or answer heel work patterns, attend to rhythmic changes, and follow the lead of dancers. At the same time, flamenco guitarists have learned to support and adorn vocal melodies by attending to the changes in harmony and melody a vocalist may decide to sing. Being able to support dancers and vocalists in performance requires a great deal of experience and a very attentive ear, and it is foundational to being able to play as a soloist because these elements drive and punctuate great flamenco guitar playing. Although not obvious to listeners who are new to flamenco, these elements are very obvious to anyone who has spent some time learning about the art form.
This last paragraph leads me to address another subject that you may want to consider as you decide on a musician for your event. Many guitarists who you will find advertising on various wedding related websites or through entertainment websites, will claim that they play several styles of music, among them flamenco. Generally speaking, either a) most of these guitarists have learned a few "pieces" from sheet music books and treat flamenco as something learned like a classical piece, or b) they play latin guitar, which is orders of magnitude simpler and usually becomes boring due to repetitious motifs and a general lack of musical variety. To someone who knows how powerful flamenco can be, this approach is sorely lacking. Because most of these guitarists have not taken the time to learn flamenco in a dance and vocal context, they don't know the basic structures and concepts that should underly their playing and it usually lacks important rhythmic details. If you want the musician at your event to engage your guests, and create a memorable atmosphere, you may want to select a guitarist who has some experience playing in a traditional flamenco context.
According to Norberto Torres Cortés, a published and highly cited author who has researched the subject thoroughly, guitar playing (including the lute and the visual) endured a split in or around the 1500s in Europe. One style embraced the Spanish technique of rasgueado, the other rejected rasgueado and favored techniques more associated with what we now call classical guitar. Modern flamenco combines and builds on nearly every technique, which makes it very challenging, yet also gives a guitarist a nearly infinite set of combinations and concepts to continue learning and with which to be creative.
Often, flamenco emphasizes many aspects of rhythm, especially in the up-tempo song forms, or up-tempo sections of certain song forms. It might be said of classical guitar, that it emphasizes harmony and melody and puts much less emphasis on strict rhythmic phrasing. It is often obvious when a guitarist is well trained in one style, and then proceeds to play in the opposite style. To accommodate a "background" ambience for certain events, I can emphasize arrhythmic song forms., It is also possible to emphasize the highly rhythmic song forms to make the feel of an event far more up-tempo. This is one area where having a someone dedicated to flamenco may make a significant difference.