We sometimes use constructions called cleft sentences when we want to focus on a particular part of the sentence. These are used both in written and spoken English.
There are two main types of cleft sentence, it- clefts and what- clefts (and a variation of what-clefts, all-clefts). What- clefts and variations on them are often referred to as pseudo clefts.
Read all about clefts and try some exercises.