1997 Honda Accord whats it called?

What is that sensor called directly above the oil filter??? because i think im leaking oil from that sensor ,,, or is that even possible??? im trying to eliminate a few possibilities of where in the hell is the leak coming from......i need to know whats that sensor called so i can purchase a new one to replace that one so hopefully it will solve the problem ...all i know is when i crawled underneath the car is that i seen that sensor and it was all covered in oil also what is that pipe going into where the water pump is?? can that pipe where it meets the engine also can leak oil ??? like does it have a gasket ??? well i dont know so if someone with knowledge can answer this i sure would appreciate it.....Thank You.....