Mbps stands for MegaBits per second and MBps stands for MegaBytes per second. These two terms may sound similar, but they are completely different. Mbps is used to specify the speed of a network whereas MBps is used to specify amount of data downloaded per second.
Well 1MBps = 8Mbps which means a 100mbps of network speed will give you around 12.5MBps of transfer speed. If you want to know the real speed of your network just divide your network speed by 8 ie. 100mbps/8 = 12.5MBps.
A good download speed would be above 25Mbps. A download speed of 25Mbps can download a file of size 10Gb in about an hour.