A tray is a thin plastic disc holder that allows a CD, DVD, Blu-ray or other disc to be inserted into the computer. In the first picture to the right, is an example of what the traditional CD-ROM tray looks like in a desktop computer. To eject this tray from the CD-ROM drive press the eject button on the front of the computer. To put the tray back into the computer just push the front of the CD-ROM tray and it will automatically go back into the CD-ROM drive.
In the bottom image to the right, is an example of a laptop CD-ROM drive tray. Unlike the desktop CD-ROM tray, this tray can be a lot more flimsy because it's thinner and is missing the right portion of the tray. Like the desktop CD-ROM tray, press the eject button to eject the tray and then push the tray back in to insert the tray back into the computer.
Other types of CD-ROM
Missing disc drive tray
Not all desktop computers and laptop computers have disc drives. If you cannot find a disc drive on the front of your desktop computer or the side of your laptop it is very likely it does not have a disc drive.
For desktop computers that have an available drive bay a disc drive can be installed into the computer. For laptop users who do not have a disc drive you can get an external USB disc drive if you want to add a disc drive to your computer.