The way I understand the difference is that the two concepts are used to give slightly different emphasis, but ultimately they are kind of the same thing. Since neither has a formal definition we cannot expect an exact answer without first limiting the scope to a particular understanding of "type" and "sort".
"Sort" is used when we want to say that there are several different, well, sorts of things that we need to distinguish. An example would be a theory of geometry with sorts "point" and "line".
"Type" is used when not only is there a need to distinguish different sorts of things, but proper attention is paid to the structure of the sorts/types themselves. Thus, typically we can form new types from old ones (products, sums, function types), we can have interesting relations between types (type equality, subtyping), etc. In contrast, one typically just specifies some sorts at the beginning, and then never pays much attention to the structure of the class of all sorts.
This at least is how I percieve the difference, other people may have different experiences.