The cello (an abbreviation for violoncello), is the true bass instrument of the string family. The double bass or contrabass is, of course, a deeper bass instrument than the cello, this is why it is called the double bass. The cello has a shape similar to a violin, but twice the size, resting on the floor supported by a spike. The player normally sits on a stool to play it.
The 4 strings are tuned to C G D A, starting from the C two octaves below middle C This is MIDI note C2. It has a range of nearly 4 octaves, up to the A in the 2nd octave above middle C.
The cello has an exquisitely beautiful velvety tone, and has been used since the baroque period as a solo instrument as well as the bass instrument for the string quartet and for the string family in the orchestra.