Alright, Damn Small Linux is a operating system about 50 megabytes big. Swap partitions I guess you could say is like memory(aka ram). Any main processes your computer does is first stored in the cache(on processor) where it is accessed the quickest. Then your middle priority processes are stored on your memory. Well, thats where swap partitions come in. It is pretty much just backup memory. If your having a heavy load on processes it is more then likely some processes will be stored on the swap partition. Granted the processes cannot be accessed as quick as with processor cache or memory, but it helps. They usually say that you need a swap partition about three times the size of your memory.
Ex. - 512 x 3 = 1536mb swap partition
I dont know if DSL comes with a boot loader. I would like to say it does, but you will have to look into that. The two boot loaders of choice are Grub or Lilo. One site that has a pretty complete tutorial on Linux is the following link.
I suggest if you dont understand some of the terms or hardware or software. Goto this site for definitions.
Before you get involved in Linux though, I say this. Linux is mainly commands. If you liked messing in DOS on Windows or you enjoy how computers work, then Linux is for you and welcome to the community brotha! DSL is a very simple and not so user friendly operating system. It doesn't have a bunch of applications or anything so it involves alot of commands. What I do recommend is Slackware. Slackware is somewhat simple to install and is easy to maintain. One thing I really like about Linux is you can have the most up to date version of a distro installed and it still runs okay. I also heard alot about Suse, Mepis, and Ubuntu. Slackware though is great for learning Linux though. It is user friendly but at the same time makes you learn all the commands and etc. Linux isn't no walk in the park but as long as you have a somewhat basic understanding of how a computer works you'll be fine. Hopefully this helps you somewhat.
Good Luck Man!