What is this?!!!!

[1997Hondacivic]

Hi,
What is This?What it for?Im asking my self this this question over and over again and a don t know for what is?What it does?
Can any one tell me

 

[civicek9]

it looks like D15z engine, and thing in red circle is lambda

 

[1997Hondacivic]

it looks like D15z engine, and thing in red circle is lambda

hi,
what it does that lambda?Thats 1.5vtec.Its of my car.

Thx.

 

[blinx9900]

Oxygen sensor, aka O2 sensor.