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It doesn't interpret anything. And if you want to be taken seriously, for God's sake, spell out "someone" instead of using txt tlk.
Cache-Control is a way to control the browser's caching. Apparently the developer thought there was an issue with Apache 2 (may be, may not be) so there's a workaround.
If the server is running Apache 2 then PHP will send one version of the header, otherwise it'll send a slightly different version. Then it sends a couple more headers. All of the above tell the browser to not cache anything.