Very simply put, fingerspelling is the act of reciting a word by forming the handshapes of each letter in sequence. Most countries with their own
sign language also have their own
manual alphabet, in which each letter is assigned a shape or location on the hands. The American manual alphabet uses just one hand to form shapes, while the British alphabet uses two hands to form shapes and point to locations on the palm.
Fingerspelling is used by both hearing and deaf individuals, usually for very different reasons. Because the alphabet is much easier to learn than an entire language, many hearing people learn to fingerspell as a means of communicating with the deaf. For deaf people, though, fingerspelling is usually just a tool. Most proper names do not have their own sign, and are generally fingerspelled. Even if an individual has a sign name, when meeting a new person they must fingerspell their name before giving their sign name. Many major cities have their own sign, but for smaller cities, street names, store names, and other such terms the word is generally spelled out. In some situations, fingerspelling is also used for emphasis - because it takes longer to state each letter of the word, the mind dwells more on that topic. Infrequently fingerspelling might be used by a signer whose free hand is occupied; if the sign won't make sense (or isn't understood) when signed one-handed, the word can be fingerspelled.
In addition to being an essential element of its language, fingerspelling is a skill, like playing the piano, that can be taught, learned, practiced, and improved. And just as not every kid taking piano lessons will become a concert pianist, not everyone who learns fingerspelling will show an aptitude for it. Both expressive and receptive fingerspelling require specific talents, using several different sections of the brain. To fingerspell, one must have a fair level of fine motor control - because the handshape for each letter is stored in muscle memory, the fingers must be physically able to form each letter quickly and on command - individuals with joint stiffness may find fingerspelling a laborious, painful process. Using it also demands that the brain be able to transform what is created in the mind as language into the physical realm. Understanding the manual alphabet is a little like reading printed words, but understanding fingerspelling can be a much larger task. Merely recognizing the letters u-s-u-a-l does not guarantee the person will realize the word is usual - the ability to instantly translate a sequence of letters into a word is much more complex, and requires effort and practice for those to whom it does not come naturally; an important tip is to watch for letter patterns rather than individual letters. The learning of quality expressive and receptive fingerspelling is so intense that Gallaudet University offers two levels of fingerspelling education, each lasting a full semester.
The Rochester method of education employed fingerspelling to teach deaf children proper English grammar, but it was considered unsuccessful and is not commonly used today.