First, let's get a few terms straight here, to avoid further confusion
a PC/laptop has, (basically) two kinds of "memory", first is the RAM. For example, my machine has 1GB of RAM installed. the other is Disk space, which allows you to save things, and load them later. For example, you save word documents to disk- windows is installed on the disk, etc.
With Optical Drives (CD/DVD drives) there are drives that can read, but not write, to the disks, (DVD-ROM and CD-ROM) and there are drives that can read/write, but not "overwrite" (that is, erase the data already there) drives, these are called DVD-R and CD-R drives, and there are disks called CD-R and DVD+R and -R that cannot be rewritten.
However, most Optical drives today are CD-RW DVD-RW drives, which can read CD-ROM and DVD-ROM discs, write to CD-R and DVD-R/+R discs, and read,write, and erase the contents of CD-RW and DVD-RW media. CD-R and DVD-R mean "recordable" and the RW means "rewritable".
When you copy photos from your camera, they are stored on your hard disk. If you want them on a Disc, you will need to "burn" a CD/DVD containing them. (it's called burning because the drive laser literally "burns" markings into the disc, by heating the surface up to around 250°–300°C). Then you can give the discs to your friends or relatives, or store them in a safe place for backup.
Adding memory to a laptop is relatively straightforward; however be sure to find out how much RAM it has compared to how much it
can have. As a example, my laptop which I bought relatively recently came equipped with 4GB of RAM. However, this is the maximum amount it supports, so I cannot upgrade past this amount. Other laptops can hold more, and/or come with less RAM, and you can often add memory later on.
In most recent laptops you can add memory pretty easily, it's usually detailed in the instruction manual. In general it means unscrewing one or two screws on the bottom of the laptop and opening a "door" too the RAM slots. Then you plop in the new memory and close it up.
You can also upgrade the disk capacity from what is included; most laptops use fairly standard HDs and you can replace them with higher capacity drives. You can also, as you said, get an external Hard disk and store your data that way.
