Question about reset vector!

I've been simulating a NIOS system in Modelsim, and I've been trying it with the NIOS II e/s/f to compare performance. I noticed that the reset vectors are different depending on which processor I use, and sometimes depending on changes to the software. I'm curious: what instructions are in the reset vector, what is their purpose, and what is different in it due to changing the type of NIOS being used?

Thanks in advance for any assistance!