A bit is a unit of classical information. It contains a boolien value. It can be 0 or 1. These values can be called many things, True or False, Heads or Tails, On or Off, High or Low. You can't do much with just a boolien value. But when many are combined, the power can be seen. Say we have two light switches. Each can be on (1) or off (0). If we say the right hand switch being on is a 1, and the left hand one is 2, we can start making larger numbers. To get the correct value we add the two values together. Thus 00 (both off)=0, 01 (left hand off, right hand on)=1, 10=2 and 11=3. Imagane for a moment, a third bit with the value of 4 when on. How high can this array go? Two important things to know about classical information, the values of the bit can be checked and copied. Thus if I have an array K I can check the value of K and I do not change it's value. Also, if I have two arrays, L,M and I want L=M I can move the bits form L to M without knowing their state or destroying it. All information most people encounter is classical and so can be broken up into bits.
There are two ways that term can be used, logical and physical. A logical Qbit is a collection of physical Qbits that make up a unit of information. There are many reasons to do this, at this point the main one is error correction. For more information see Error Correction.md (When it is updated.)