Another user on the forums opened up their tablet and there ARE actually 2 x 128 MB DDR memory chips on the board. However, much like a desktop computer or many laptops the memory on the board is "shared" with built-in features like on-board video, audio, etc. By the time on-board devices are done, and whatever is allocated to the operating system, you get what's left to run your apps.
one more question, can I make a big space for app or system in this tablet?
so I can install many application on my haipad?
Just so it's clear, that question is about the STORAGE chips, not the RAM chips.
When you install apps they are put into the /system/app/ folder (unless you are using third-party applications that let you install apps to your SD card, which has it's own drawbacks).
Only *some* of the apps in that folder can be safely removed to free up space, and you may need to use ADB to do it (if they are preinstalled apps you'd most likely need to use ADB to mount the file system read/write and remove the apps via adb shell commands).
The internal storage chip is like a hard drive that has been partitioned into a bunch of smaller logical drives. By default most of them are "read only" so even if there is space in the partition you generally can't use it. The partition maps can be rewritten (as some people have learned by flashing the wrong firmwares) but unless you're a custom rom cook you won't be messing with partition maps.
I'm not sure how much space is available in the /app/ folder for your apps. The /nand/ folder is the one that can be mounted as a USB flash drive to your desktop computer, but you can't install apps into it. It's just for transferring documents, photos, videos, or other files to your tablet if you don't have (or don't have space on) a SD card.
I believe it's called "Apps 2 SD" (A2SD) and involves partitioning an SD card. I haven't used it and don't know how to set it up or make it work. Downsides to running apps from the SD card are, of course, you can't use the app if you take the card out (so you have to leave it in all the time), it reduces the storage space on the SD card, it can make the SD card run hot. I'd also imagine it's more prone to data corruption than the internal storage is.
I'm pretty sure that /nand is actually it's own partition with read/write privileges, while /system is another partition that mounts read-only. You'd have to change the partition map. Unless you're cooking your own custom rom you won't be changing any partition sizes.
The /nand storage is for your documents, photos, videos, game data, etc. and in some cases only if there isn't an SD card available (but some apps won't use that space even if it is available, they'll only write data or cache to an SD card). The SD card is the ONLY place you have ANY control over how much space there is (by what size card you buy). As I mentioned, there is an option to install apps to the SD card.
If you install apps to your SD card you can offset that loss of space by putting everything else that you can in the onboard /nand storage.