Loading SRAM,SDRAM or FLASH on DE1, using Linux, without Qsys, SOPC or NIOS

Guys,

I have some doubts.

I'm building a system based on another one that I have (DE2_NET - it is in DE2 CD ROM), so I'm trying to understand what the function of each memory element.

We find these in the project (one of each):

Avalon MM Tristate Bridge

Flash Memory

EPCS Serial Flash Controller

SDRAM

The Resect_vector is pointing to Flash Memory and the exception_vector to SDRAM.

My doubts:

I think that the the .elf is being downloaded to the flash memory, I'm correct?

1. What's the function of each one?

2. Why I need to use EPCS?

3. I only can use flash memory whe I'm using a Avalon MM Tristate Bridge?

Ps.: I'm reding some documentations but the differences are still not clear.

Thanks