If you’ve ever wondered, and didn’t know how to check, here’s a useful website: Speakeasy.
By measuring the download and upload rate from the 8 locations in the USA you will be able to accurately measure your current line throughput or Internet connection speed.
They also have good explanations for the not-so-geeky people:
Download is a measure of how fast your connection delivers content to your computer or local area network.
Upload is the measure of how fast content is delivered from your computer or local area network to others on the Internet.
To achieve optimal delivery of T1 or SDSL services, download and upload speed should match or at least be very close. This is very important for applications like VoIP, email, on-line gaming and other interactive programs. Upload speed is even more important if you are operating an email, web or file server at your location.
Kbps transfer rate = kilobit per second transfer rate. There are 8 bits in a byte, so we would divide kbps by 8 to get KB/sec transfer rate.
Check also what Speed Test is about here.