The IDC 50 connector is a 50-pin 8-bit SCSI "header" connector used for internal-type ribbon cables.
It is also known as the "Alterative 2" connector.
It has parallel 25-pin rows and resembles an older ATA/IDE drive cable except that it is wider and has more pins.
The HPDB 68 connector is a 68-pin 16-bit SCSI-2 connector used for both internal and external connections (plastic for internal and metal for external).
It has parallel 34-pin rows but has the pins much closer together and is therefore narrower than the IDC 50 connector.