Seshat was the goddess of wisdom, writing and measuring. She was also in charge of keeping records, astronomy and architecture. Writing was sometimes said to have been invented by Seshat. She had many functions in common with Thoth.
She is well-known for determining the number of regnal years of a king and recording his name on the leaves of a tree. She also was involved in the celebration of the (theoretically 30 year) jubilee of a king (the so-called Sed festival).
Together with the king she would lay out the foundations of a temple as one of the first steps in building it; Seshat and the pharaoh would perform a ritual called "stretching the cord", determining both the dimensions and the alignments of the future structure.
She can also be seen recording the inventory / booty and the number of captives during military campaigns.
Seshat is usually shown as a woman wearing a seven-pointed star with two horns (pointing downwards) on her head; this has not yet been explained in a satisfactory way; it was suggested that the star on its stem is in fact a stylised papyrus plant (symbol of writing), above which can be seen a crescent moon (possibly derived from Thoth), which later became two horns.