The Law School Admissions Test, or LSAT, is designed to assess skills considered necessary for success in law school.  It does not measure your familiarity with certain subject material, but rather your ability to understand and analyze new information, organize your findings, and draw logical inferences from them. 

This test is a crucial part of the law school's admissions process and will be one of the most important factors determining whether or not you are admitted to your preferred law school.

You can sign up to take the LSAT at the website of the Law School Admissions Council.