Is -OH group + inductive or - Inductive? Explain the relative acidic strength of o,p,m-hydroxy benzoic acids?

The OH group is a strong electron-donating group, which increases the rate of electrophilic substitution, hence it has a positive resonance effect or it is +R. On the other hand, because the C-O bond of the phenol is polarized towards the oxygen, it creates a small positive dipole on the aromatic ring, which retards electrophilic substitution. Since the inductive effect is weak, in comparison to the resonance effect, and it tends to have a negative effect on electrophilic substitution it's name - I.

I hope that explanation clears your question. As far as the acidity of the carboxylic acid, you have to look at the stabilization of the conjugate base. Both ortho and para OH groups destabilize conjugate formation due to their resonance effects; while the resonance effect of the meta substituent only destabilizes formation of the conjugate by a small fraction. From this discussion, we would expect the acidities to be:

meta > ortho~para

however, the ortho isomer has another attribute that is of great importance: its inductive effect. Because of its location, the hydroxyl group of the aromatic ring can hydrogen-bond with the proton of the carboxylic acid and because this effect serves to stabilize the transition state, it wins over its resonance effects, thus the observed acidity strength is:

ortho (pKa=2.98)> meta(pKa=4.08) > para(pKa=4.58)