What does __section( ) mean in linux kernel source

I see the following code in some OS kernel. But I don't understand the way __section is used, and don't know what does this code mean.

#define KEEP_PAGER(sym) \
    extern const unsigned long ____keep_pager_##sym; \
    const unsigned long ____keep_pager_##sym  \
        __section("__keep_meta_vars_pager") = (unsigned long)&sym