What does zRAM mean? I heard about a feature called zRAM in the new Android ROMs.

Does anybody have detailed information about it?
According to post over the XDA thread: 

In order to explain more precisely ZRAM first need other terms are more clearly defined:
Swap can be compared with the swap file on Windows. If the memory (RAM) to complete the PC the data that are being used not actively outsource (eg:background applications) so as to re-evacuate RAM free. To this data is written to a hard disk. If required, this data is then read back from there easily. Even the fastest SSD is slower than the RAM. On Android, there is no swap!

In ZRAM unnecessary storage resources are compressed and then moved to a reserved area in the fixed RAM (ZRAM). So a kind of swap in memory. This Ram is more free because the data then only about 1/4 of the former storage requirements have. However, the CPU has to work in more because they compress the data has (or unpack again when they are needed). The advantage clearly lies in the speed. Since the swap partition in RAM is much faster than this is a swap partition on a hard drive.

In itself a great thing. But Android does not have a swap partition, and therefore brings Android ZRAM under no performance gain as would be the case with a normal PC.

In normal PC would look like this:
Swap = swap file (on disk) -> Slow
ZRAM (swap in RAM) -> Faster than swap
RAM -> Quick

With Android, there is no swap partition, and therefore brings ZRAM also no performance boost.
The only thing that brings ZRAM is "more" RAM. Compressed by the "enlarged" so to speak of the available memory. That's on devices with little RAM (&lt;256MB) also pretty useful. The S2 has 1GB but the rich, and more than. There must not be artificially pushed up to 1.5 GB. After you activate the ZRAM also has 2 disadvantages. The encoding and decoding using CPU time, which in turn has higher power consumption.

Roughly one can say (For devices with more than 512MB RAM):
Without ZRAM: + CPU Performance | + Battery | RAM
With ZRAM: CPU Performance |-Battery | + RAM

For devices with too little RAM so it makes perfect sense. But who shoots the S2 already be fully complete RAM and then still need more?

I hope it helps to understand zRam!!!!