What is launchMode "Multiple"?

What is "multiple"

It is a noun (or, alternatively, an adjective, depending upon usage). :-)

and what happened to "standard"?

In that one spot in the docs, it was replaced by the word "multiple".

So is "multiple" just a typo?

I am assuming so. It is possible that they renamed it, and standard and multiple will mean the same thing, though that too is a documentation bug, which is why I filed the issue (see link at beginning of this paragraph).

Nice catch!

Probably it is just a typo. E. g. constant in ActivityInfo class is named LAUNCH_MULTIPLE but the comment says:

Constant corresponding to standard in the launchMode attribute.