One way of understanding personality development is through the use of stage theories. Probably the pre-emiment version of such a stage theory is that by Eirk H. Eirkson. Erikson's model was an extension of Freud's work:
Freud's Stages of Development
To learn about Erik Erikson's Stages, you can look at the page on Erikson from George Boeree's on-line theories textbook. There is a chart of Erikson's stages in the middle of the somewhat lengthy page:
Erik Erikson and his Eight Stages (from George Boeree)
Another site that explains Eriksons stages is this one from the Child and Parenting Development Center On-Line.