Illumina HT12 v4 are human gene expression arrays. Typically these arrays are used for differential gene expression analysis. Copy Number, SNPs, and mutations are not the target of these arrays. At a fundamental level, the arrays are a collection of oligonucleotide beads, with probe sequences targeting different genes. Each bead is replicated (~20-40 beads per probe). Typically bead level observations are collapsed down prior to analysis, giving a raw probe expression, along with the bead standard deviation of that expression. I'd definitely do some more reading, there's plenty of information about these as linked above.