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Extracts information about a process from the processes memory that is eather hard to find or not in any other location.
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Up until recently I thought that the information in /proc/$$/environ was the current environment for that process. However it is actually the environment of the process at execution time. The environment is initially stored in the processes stack. If the process modifies its environment Linux maloc's new space and copies the environment to the heap and updates the environ symbol to point to the new location.

One of the functions that gets run when a process starts is the create_elf_tables function. This function creates and populates a mm_struct. This structure, among other things, contains env_start and env_end, which are the memory address of the beggining and end of the environment variable data. The proc file system reads this information from the mm_struct when the environ_read function is called. So the proc file system is giving you the environment at execution time and not the current environment. Also the gdb command "who environ" also gives you the environment at execution time (I am assuming its doing the same thing but i have not looked into it yet). You can get the address of the environ symbol from gdb and get the data that way.

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