Internet speed is a combination of bandwidth (download and upload) and latency.  Bandwidth measures the size of the "internet pipe" and latency how long of delay exists for information to move through the pipe.  The LARGER the bandwidth (size of pipe) the faster the internet connection will feel.  The LOWER the latency (amount of delay) the faster the internet connection will feel.  This means you can have very a high bandwidth, of say, 100Mbps, but high latency and your internet connection will still feel very slow. 

Think of it like a highway system.  The number of lanes would be equivalent to the size of bandwidth.  More lanes (bandwidth) allows more cars (data) to pass through.  Latency describes how long it takes for the car (data) to first show up onto the highway.  With high latency, the data simply takes longer to get moving!

Latency - The delay in processing data over an internet connection.  Low latency = less delay.  High latency = more delay.  Typical latency on a cable internet connection can be 100 milliseconds (ms) or more.  Typical latency on a fiber connection is less than 30ms.  

Download - The amount of data that can be sent TO your computer/device in a set amount of time.  This is measured in megabits per second.  When you are reading emails, visiting websites, streaming video or music, this is all "downloading."

Upload - The amount of data that can be sent FROM your computer/device in a set amount of time.  This is measured in megabits per second.  When you are posting pictures/videos, add attachments to emails, or save files to the cloud this is "uploading."  

When stated together, the download and upload bandwidths are shown like this:  100/5 (indicates a 100Mbps download bandwidth and 5Mbps upload bandwidth).  Internet service providers typically only advertise their download bandwidth as they utilize asymmetrical systems where the download and upload are not the same.  An all fiber system such as PeakFiber, is symmetrical meaning the download and upload are identical.  PeakFiber offers 50/50, 100/100, and 1,000/1,000 services.  Go fiber!