The partition table is a part of the MBR of a PC-type hard disk. It is an array of four 16-byte entries. A detailed break down is already discussed in an linked article included in the previous subsection 2.1.
The main purpose of a partition table is to logically divide a hard disk drive into smaller portions called partitions. Amongst other attributes, a partition has a start, an end and a type. The bootstrap code of an MBR needs the partition table so that it knows where to find an operating system to complete the bootstrap operation.