CE Benchmark is an ExpressionEngine® plugin. This means that it does not have a user interface, but is intended as a development tool to be used in your templates. It allows you, as the developer, to dynamically place markers in your template, and then retrieve the time it took to execute the code from one point to another.
Because it allows you to easily compare the speed impact that code changes in your template can have. It is a handy tool when performance-tweaking your sites.