Deer only eat plants. Lions only eat meat (On the other hand)
Deer eat only plants. On the other hand, lions only eat meat.
Some mushrooms are safe to eat. Other mushrooms are poisonous and should not be eaten. (in contrast)
Some mushrooms are safe to eat. In contrast, other mushrooms are poisonous and shouldn't be eaten.
My hometown is small and historic. Your hometown is small and historic. (be similar to)
My hometown is similar to your hometown.