Everything from the 1 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
A halogenoarene has a halogen atom bonded directly to a benzene ring. Chlorobenzene is made by electrophilic substitution: benzene and Cl2 with an anhydrous halogen carrier (AlCl3 or FeCl3) at room temperature; methylbenzene gives a mixture of 2- and 4-chloromethylbenzene. Chlorobenzene is much less reactive towards nucleophiles than chloroethane. A lone pair on chlorine overlaps with the delocalised π system, giving the C–Cl bond partial double-bond character, so it is shorter and stronger (about 0.170 nm against 0.177 nm), and the electron-rich ring repels an approaching nucleophile. So chlorobenzene gives no reaction with NaOH(aq) on warming and no precipitate with ethanolic AgNO3, but its ring still undergoes electrophilic substitution at the 2- and 4-positions.
Do not write a halogen carrier for side-chain chlorination: AlCl3 puts Cl on the ring; UV light puts it on the CH3. Chlorobenzene is unreactive because the C–Cl bond is stronger (lone pair delocalised into the ring), not because Cl is less electronegative, and the ring repels nucleophiles. Never say chlorobenzene gives a white precipitate with AgNO3. When asked for the products of ring substitution on chlorobenzene, give both the 2- and 4-isomers.