A pound is 20 shillings, and as there are 12 pence to a shilling (aka sovereign), is also 240 pence. Five shillings make a crown, 2½ shillings a half crown and 2 shillings a florin. 21 shillings is a guinea.
Below shillings are sixpence, twopence (“tuppence”), pennies (pence), half pennies (ha’pence) and farthings (¼ pence).
It’s quite difficult to convert Regency money into present day equivalents, but Dr. Joan Klingel Ray in her excellent Jane Austen for Dummies takes a stab at it using the calculator at MeasuringWorth.com.