Total depth of coverage per sample and over all samples.
INFO=<ID=DP,Number=1,Type=Integer,Description="Approximate read depth; some reads may have been filtered">
This annotation is used to provide counts of read depth at two different levels, with some important differences. At the sample level (FORMAT), the DP value is the count of reads that passed the caller's internal quality control metrics (such as MAPQ > 17, for example). At the site level (INFO), the DP value is the unfiltered depth over all samples.
See the method documentation on using coverage information for important interpretation details.