Could Someone Clearly Define What A Gene Variant Is With An Example

Question

[vigprasud]

Could someone clearly define what a gene variant is with an example. I am totally confusing myself with SNPs, alleles, variants and how the major and minor allele are defined. A clear example with gene names will be really helpful.

[Pierre Lindenbaum]

ask http://biology.stackexchange.com/

[Sean Davis]

What is SNP calling?