At around 3 or 4 years old, kids may start to practice writing, and included among the scribbles may be recognizable letters. For example, you may notice your child writes all of the letters of his or her name in a seemingly random way on different parts of the piece of paper. That's because kids learn to write individual letters before they learn how to put them together to form a word.
As they continue to read and develop an understanding of how words work, kids start to understand how to group letters into words. Between kindergarten and first grade, most learn to put letters together into words and will use these words to label pictures that they draw. Kids this age usually use only capital letters and will not include spaces between words. They will also use "invented spelling," writing words with no vowels (for example, BBYDLL for baby doll).
Eventually, with practice and formal schooling, kids learn what are called the conventions of print — writing from left to right, the difference between upper- and lowercase letters, how to put spaces between words, and how to use correct spelling in most instances.
As your child gets older and develops more motor control, his or her handwriting will become smaller and neater. Between second and fourth grade, kids learn to write in cursive and will apply the conventions of handwriting automatically.