This clearance provides access to information or material that may cause "serious damage" to national security if it were released without authorization.
For example: This information could refer to plans to conduct a tactical combat operation. The plans might cover only a single operation in a limited area for a very limited period of time. However, premature disclosure of this information could hurt the success of the operation.
To obtain a Secret Clearance, an individual must pass a "National Agency Check with Local Agency Checks and Credit Check" (NACLC), which looks back at the last five years of your life. A Secret Clearance must be renewed every 10 years.