Broad Benchmarks are assigned based on the 4 Broad Asset Classes. These are used in "relative to benchmark" calculations such as Tracking Error, Information Ratio, etc.
There are 4 broad benchmarks:
S&P 500 Index is used for Domestic Equity
MSCI EAFE is used for International Equity
Lehman Brothers Aggregate Bond Index is used for Taxable Bond
Lehman Brothers Municipal Bond INdex is used for Municipal Bond