These inserts have external threads so that they can be threaded in. They work in a similar way to coiled inserts but are solid. Some people find these easier to use than the more fiddly coiled version and also think them stronger. It often comes down to personal preference for the particular application.
The threads on this type of insert do not need to match internally and externally; they have a wall thickness which allows them to be threaded separately.
However, it is possible to get thinner walled inserts with matched threads.
These inserts are available for use in metal and some woods.