You will be told the speed that your ISP provider will be trying to provide you service when you sign up. These speeds are best effort so they may not get you actually that speed.
If you discover your speed is substantially below the speed quoted by them you can try turning your modem/router on and off and if still low call your ISP for assistance. The problem may be in your equipment or in their equipment or lines.
Two places that I have used to test my actual speed are www.2wire.com and www.speakeasy.net These will work on DSL, cable, satellite or whatever connection you have.
When you go to www.2wire.com at the top is a link for Speed Meter. Go there. It will automatically test your download speed and gives the ability to retest.
At www.speakeasy.net you will get more information on your speed. It measures not just your download speed (the one advertised normally) but also your upload speed which will be less than your download speed. When you get on the site look in the middle of the page for Speed Test and click on it. Then on the next page choose the location closest to you and the test will run and give you both the download and upload speeds.