Notation question

[stardust1611]

I came accross some strange sheet music notation in some of the Bach's works, like for example in Fantasia and Fughetta BWV 907. On some notes on the base staff, there are stacks of numbers over a single note. Sometimes there is one, sometimes two and sometimes three numbers. What do they mean, and how to play it?

[stardust1611]

I just found the answer on this page: https://en.wikipedia.org/wiki/Inversion_(music). It's called: figured bass. But, if you have something to add, please do!