In: Chemistry
In this case, phenol is considered as a major group and numbering is given with respect to -OH group.
In ortho-bromo-4-tert-butylphenol, -Br group is at second position and ter-butyl group is at fourth position. Here -Br group is ortho i.e. two substituents occupy positions next to each other.
In meta-bromo-4-tert-butylphenoll, -Br group is at third position and ter-butyl group is at fourth position. Here -Br group is meta i.e. the two substituents occupy positions 1 and 3.
The structures of ortho-bromo-4-tert-butylphenol and meta-bromo-4-tert-butylphenol are shown in image below