RefTeX can be configured to recognize additional labeled
environments and macros. This is done with the variable
reftex-label-alist (see Options - Defining Label Environments). If you are not familiar with Lisp, you can use the
custom library to configure this rather complex variable. To do
M-x customize-variable <RET> reftex-label-alist <RET>
Here we will discuss a few examples, in order to make things clearer.
It can also be instructive to look at the constant
reftex-label-alist-builtin which contains the entries for
all the builtin environments and macros (see Builtin Label Environments).