They are commonly formed via the  Williamson synthesis in which an alkoxide attacks an alkyl halide through an SN2 mechanism to form both symmetrical  and asymmetrical versions.
A version of this type of compound that includes silicon is commonly used as a protecting group for hydroxyl groups, while the crown variety is synthetically useful to form complexes with metal cations. They are commonly formed via the  Williamson synthesis in which an alkoxide attacks an alkyl halide through an SN2 mechanism to form both symmetrical  and asymmetrical versions. Epoxides are a cyclic version of them, with the simplest being ethylene oxide. FTP, name  this functional group, an oxygen atom single bonded to two carbon atoms.
A version of this type of compound that includes silicon is commonly used as a protecting group for hydroxyl groups, while the crown variety is synthetically useful to form complexes with metal cations.
ether