What is this fluid container?

[Rkahut]

i have a 1986 rx 7 ok im a big noob with cars, so when i pop the hood now i know i have my clutch fluid and break fluid, and oil on the top right side, and my rad fluid on the bottom but this is where im puzzled because i could not find this in the manual i have this other fluid in the very very top left corner errr if anyone could give me a hand on what this is that would be much help thanks!! looks a bit low and i would much like to fill it up quite soon!!!