Version Control: Do you need both TortoiseSVN and Subversion?

Installing a version control system for my local machine left me confused. Did I need Subversion and TortoiseSVN? If TortoiseSVN is only a “client” can it work without Subversion? If it can’t, why does TortoiseSVN allow me to create repositories without me having installed Subversion yet? After having wasted a day googling, good sense prevailed [...]