Though you may hear both terms in reference to DNA, genotyping and sequencing refer to slightly different techniques.
Genotyping is the process of determining which genetic variants an individual possesses. Genotyping can be performed through a variety of different methods, depending on the variants of interest and the resources available. For looking at many different variants at once, especially common variants, genotyping chips are an efficient and accurate method. They do, however, require prior identification of the variants of interest.
Sequencing is a method used to determine the exact sequence of a certain length of DNA. You can sequence a short piece, the whole genome, or parts of the genome such as the "exome," which are the regions of the genome that contain the instructions for RNAs (ribonucleic acid) and proteins. Depending on the region, a given stretch of sequence may include some DNA that varies between individuals, in addition to regions that are constant. Thus, sequencing can be used to genotype someone for known variants, as well as identify variants that may be unique to that person.
Historically, 23andMe has offered reports using genotyping technology. The specific positions we look at are known to more commonly vary between individuals that span the entire genome. All reports in our Personal Genetic Service are based on genotyping technology. However, we now also offer reports using sequencing technology through 23andMe+ Total Health.
For example, our Personal Genetic Service provides a genotyped report, the BRCA1/BRCA2 (Selected Variants) Genetic Health Risk report, which looks at 44 different variants within the BRCA1 and BRCA2 genes that are known to be highly penetrant. Our 23andMe+ Total Health membership provides an exome sequencing report that looks for thousands of variants across the BRCA1 and BRCA2 genes, in addition to thousands of variants in many other genes associated with increased cancer risks.