DSL service essentially "piggybacks" on a regular phone line, letting that line serve both voice and broadband independently; you can have one phone line, one phone number, your 'puter is online all the time (if you want it to be), and your voice phone works just as it always did. Typically, DSL will offer nominal throughput speeds of 512 down and s56 up, though there are other configurations, depending on what your DSL pprovider offers. If you have, or have considered, a separate phoneline for your 'puter, to keep your voice line free during those long surfing sessions, you'll probably find DSL service amounts to pretty close to the same money considering the cost of a second phoneline and the cost of a standard dialup internet account together. Given the speed advantage, DSL comes out way ahead of dialup if you're a heavy 'net user.
Cable internet is provided over the same system used for cable TV, and while it usually is bundled with cable TV service, it can be standalone in most markets. Cable internet usually is nominally faster than DSL, though if the circuit you are on has lots of users, a bunch of whom are prone to be online at the same time, or a few of whom generate particularly heavy traffic themselves, slowdowns can be noticeable.
Either DSL or cable are orders of magnitude better than dialup if you do much more than simple web browsing and emailing. Not all areas are served by DSL or cable; check your local phone book for internet service providers to see what is available to you, or check online for broadband providers serving your neighborhood. As far as security goes, its really no different no matter what sort of connection you use. A current antivirus is a must-have, you should have a decent firewall, and an anti-spyware app is a good thing to have.
A good website for further research into broadband options is
BroadbandReports
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