The SAT IIs are one hour multiple choice subject tests which many schools require. Most schools which require them want them as well as the SAT I, some schools may want them in place of the SAT I. The SAT II subject tests used to be called the Achievements. As of the graduating class of 2012, the UC system no longer requires the SAT II subjects tests, but they will be recommended for some majors.
These are tests on individual subjects such as literature, math, biology, US history, chemistry, Spanish, etc. The SAT I does not require the student to bring in any outside knowledge of a subject other than having the skills necessary to solve the problems. This is not true of the SAT IIs. For example, a question on the US history test may ask you to recognize which president implemented specific legislation. The literature test requires knowledge of literary terms such as metaphor.
Math Level 1**
Math Level 2
French with listening
German with listening
Spanish with listening
Chinese with listening
Japanese with listening
Korean with listening
Notice that some of the languages can be taken with or without listening, some cannot be taken with listening (Italian, Latin and Hebrew), and lastly, some can be taken only with listening.
** Some schools will only accept the math level 2 for a required SAT II. Check the universities you are applying to before you take math level 1.