The structure of this molecule is an anisole with bromine group attached to the secondcarbon and an ethyl group attached to the 5th carbon in the parent chain.
The 2-bromo-5-ethyl represents functional groups and the anisole represents the parent chain. This anisole is a benzene derivative with a methoxy group which is attached to the benzene ring.
So, the parent chain of 2-bromo-5-ethyl is anisole. The functional groups are bromine group at 2nd carbon and ethyl group at the 5th carbon in the parent chain.