Parenthesis is a specific term used within writing lessons, when additional information is inserted into sentences. This can be done using three different pairs of punctuation marks.
Bournemouth has a very long beach.
Bournemouth, situated on the south coast of the United Kingdom, has a very long beach.
Bournemouth (a large town in the United Kingdom) has a very long beach.
Bournemouth – located within the United Kingdom – has a very long beach.