They can also be external.
Most likely you will have to reinstall the drives for the CD and DVD units
To make them easy to upgrade.
An Optical Bay is a designated space within a computer, typically a laptop or desktop, designed to hold optical drives such as CD, DVD, or Blu-ray drives. In many modern devices, this bay may be repurposed for other uses, such as additional storage drives or solid-state drives (SSDs), especially as physical optical media becomes less common. Users can often replace the optical drive with an adapter to install other hardware, enhancing the device's functionality.
A Molex Connector connects to optical drives and hard drives.
CD and DVD disks are used by optical disc drives.
According to http://www.answers.com/optical+drives, David Paul Gregg developed an analog optical disc for recording video and patented it in 1961 and 1969.
Hot swappable means the same thing whether the computer is a laptop, desktop or server. It means that you can remove and replace a drive (hard drive or removable media) while the computer is running.
You can not only use optical cleaning cloths on your laptop, it's actually recommended as it's not abrasive.
It is called an optical drive because the mechanism for reading and writing information is optical (light) based - it uses lasers.
Monitors, Printers, NIC's, Hard Drives can be both, and optical drives.
You can install them the same way as all other hard drives to your laptop. You can put the CD into your laptop and install it or you can put in the USB cord and install it like that.
Enhanced Integrated Drive Electronics (EIDE)