bool is a compiler alias of System.Boolean, int is System.Int32 etc, so when you type just "bool", it is converted to "System.Boolean".
https://msdn.microsoft.com/en-us/library/ya5y69ds(VS.80).aspx[
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Also I found the answer to your question in seconds by googling "bool vs system.boolean", read the FAQ and please do your own basic research before asking a question.