As Ice Wolf says, bis is used in house numbers in the same way that “a” is added to a number.
I trained as a chemist, so will also point out another use of “bis” - it’s used in chemical names to mean “twice” in the same way as the “di-” prefix, to show that there are two of a particular unit. However, whereas you use “di-” for a simple unit (eg methyl, as in 2,2-dimethylbutane), you use “bis” where the unit that is repeated is itself a complex structure, as in 2,4-bis(2,2-dimethylbutanyl)phenol.
Just on the word “encore”. I’ve seen etymologies point to Sir Richard Steele being the first to use it in a piece published in the Spectator of 1712, but it apparently came from 1710 and operatic performances at the Haymarket.
It’s also used in some legal traditions, notably the civil law tradition and international law. If a statute or international covenant is amended by adding an entirely new article, it’s sometimes given the number of the article it follows, with “bis” added on.
So if the International Kumquat Treaty is amended by adding a new article right after article 20, the new article may be cited as “International Kumquat Treaty, art. 20 bis.”
In some uses, it has taken on the meaning “modified version” (I would guess from the extension of “encore” to indicate “second try”).
Examples would include the practice of improvements in French aircraft and projects and programs by governments in which the implemented plan is a modification of the first proposal. (The latter is quite close to the example Northern Piper presented, except that I have seen it used in private corporations and in projects that were not laws.)