Many of us take for granted that not everyone has the technical know-how to understand the different options that are available for home internet service. These days, there are four predominant technologies - DSL, Cable, Satellite, and Wireless (Celluar/3G/4G/WiMAX/etc). Each one has benefits and downsides that you should be aware of before chosing what fits you best.
DSL is the backbone of home internet from the phone company (Verizon, AT&T, Qwest, etc). It has its roots in the POTS network and is extremely mature at this point with speeds as high as around 20mbit down and 1mbit up. It is called ADSL because the download and upload speeds are different - this works well for home users who download more content then they upload.
Advantages: Mature technology, 'dedicated' bandwidth, wide variety of equipment including business class modems/routers. Can support the activities of 1-5 people (average size household) without serious performance problems.
Disadvantages: Pickey about line quality, can be unstable during bad weather if water leaks into lines. Upload speeds are reasonable, but many providers only go between 256kbit to 768kbit. Needs DSL filters on each extension in household or calls will disconnect/interfere with the modem. Incompitent technical support (usually outsourced).
Like DSL, cable is a backbone of home internet services. Provided by cable companies (Comcast, Optimum Online, etc), it is a fairly mature technology and with DOCSIS 3.0, transfer speeds can reach 30mbits and higher. Also, like DSL, download and upload speeds are different and can vary depending on coax quality and time of day.
Advantages: Mature technology, fast download speeds (see below for catches), fairly reliable, and supports average sized households and small businesses with ease. Upload speeds are usually higher then DSL.
Disadvantages: Cable company politics of transfer caps that either cause overage charges or outright termination of services. Limited equipment choices for modems. Shared bandwidth among neighborhoods - when one person gets greedy with bittorrent, the whole neighborhood suffers. Very sensitive to line splitters - if too much dbi loss is present, modem will disconnect often. Incompitent technical support (outsourced).
A fairly recent affordable consumer technology, Satellite internet relies on satellites orbiting the earth to 'beam' internet to you. Gas stations, convience stores, and other small businesses have used this technology to provide uplinks for their registers and credit card machines to corp offices for years.
Advantages: Works almost anywhere as long as you have a clear line of sight to the sky. Not dependant on cable or telephone service.
Disadvantages: Could go on for several pages, but the short list is... Unreliable and affected by weather and wind which can obstruct the view of the sky or blow the dish off direction. 500ms to 2-3 second latency - completely unusable for online gaming or any service that requires interactivity. Absurd transfer caps (some as low as 100-200MB a week) that anyone who does even the slightest bit of web browsing will go over the first day. Unresponsive and incompitent technical support. Fixing dish problems require a visit from a tech with special equipment. High price for very little service. Special proxy settings required or web browsing speeds are horrible. Can only support one user reliably.
The most recent of the internet access technologies, Wireless offers many of the benefits of DSL and Cable without being tied down to a specific location. Speeds can vary depending on technology, but usually offers 512kbit to 2mbit download. Comes in form factors from ExpressCard to actual modems that look like DSL and Cable modems and connect to desktops through ethernet. Most cell phone companies offer data plans using technology such as EV-DO, LTE, WiMAX, aka 3G/4G.
Advantages: Works anywhere your provider has service. Higher latency then cable or DSL, but lower then Satellite. Can support 1-2 users without too much issue. Different form factors for modems for use in desktops or laptops on the go.
Disadvantages: 5GB transfer limit monthly on most plans. Depends on signal quality - if your cell phone doesn't work inside your house, don't expect the wireless modem to work either without an external antenna. Speeds vary based on how far you are from the local cell tower for your provider. Equipment quality can vary based on vendor. Extra software required on laptops for ExpressCard and USB modems.
So, which is the best option for you? It all depends on what is available in your area, and what you are willing to pay. If you have the choice, DSL or Cable is the best choice.