The smallest unit of measurement on a computer is the bit. There are almost always eight bits in one byte. These two terms are commonly confused with each other.
To compound the confusion, the abbreviation for bit is a lower case b, while the byte is abbreviated with an upper case B.
Making things even more complicated, all the compound forms of bits and bytes are kilobyte (KB), megabyte (MB), gigabyte (GB), etc. It can refer to two different values. Sometimes you will see kilobyte and it means 1000 bytes, while it can also mean 1024 bytes.
One other important thing you should know is that whenever you hear about the speed of an internet connection, it is almost always going to be referred to in bits, whether that is kilobits, megabits or gigabits.