DNA sequencing is a process used to determine or identify the order in which nucleotides are present in a DNA sequence.  These are two main types of DNA sequencing methods: Sanger sequencing and Next Generation sequencing.
Sanger sequencing, also known as Shotgun sequencing, is capable of sequencing whole chromosomes or long DNA strands with more than 1000 base pairs. In this method, the target DNA is copied several times, making fragments of varying lengths. Fluorescent “chain terminator” nucleotides mark the ends of the fragments and allow the sequence to be determined. Sanger sequencing is expensive and efficient for larger-scale sequencing.
Next Generation sequencing, also known as high-throughput sequencing, refers to newer, larger-scale approaches that are capable of producing thousands of sequences simultaneously. This increases the speed of DNA sequencing while lowering its cost significantly.