The 23andMe V4 chip is 23andMe’s fourth microarray chip and is the one now in use. It replaced their V3 chip in November 2013. It is a completely custom Illumina Genotyping BeadChip.
The 23andMe V3 chip was 23andMe's third microarray chip. It replaced their V2 chip in January 2011. It was a custom version of the Illumina OmniExpress Genotyping BeadChip. One of its key features was backwards compatibility with their V2 chip.
The 23andMe V2 chip was 23andMe’s second microarray chip. It is almost surely the Illumina HumanHap550 Genotyping BeadChip.
23andMe raw data files are downloaded in the ZIP format. This is how you extract them for use by some 3rd party sites like James Lick's mtDNA page.
Many 3rd party utilities need you to download your results from 23andMe to use them.