2005 Nissan Frontier Engine Bay Part Identification

I am not an advanced mechanic by any means but am trying to resolve my issue. For the last two weeks when I drive my frontier for about 20 minutes a strong odor comes from the passenger side engine bay. I had checked all fluids and they all were within normal ranges. I had the truck on for 30 minutes or so commuting to work and I saw white smoke come up from the passenger side when I pulled into work. I shut off the truck and opened the hood and saw a fluid leaking and hitting the hot manifold turning the liquid into vapor/smoke. The smell was defiantly coming from the leak. I tried to turn the truck back on that evening when I got off after checking fluids and it would not start. I removed cables from battery terminals and it started right up. The part that is leaking the fluid is also releasing pressure due to me being able to hear it coming out with a very slow drop pattern of fluid. I have looked all over online and can not find out what this part is. I'm hoping someone can identify it and inform me as to what it is called. It doesn't seem to be hard to replace but am welcome to all advice/knowledge. (Truck has not been driven since the leak was found to prevent any further damage.) Thank you.