What is the difference between entender with preposition 'a' and without it

Question

entender a su hijoentender su pinto de vistain english we don't use any preposition with the verb 'understasnd'but why in spanish, do we use preposition 'a' sometimes?

Accepted Answer

This is the personal a which is used in Spanish.
The personal a is used before direct objects. The personal a is generally used when the direct object is a person, or an animal or thing that is thought of as a having personal qualities.
There are a couple of lessons on here which will give you further explanations.

Answer

Hola Irigasumi
Following Marsha's comment, here is a list on some personal "a" verbs and a list of some common verbs that take the "a" when having "people" direct objects. 
I hope it helps, 
personal a verbs
personal a verbs list
Saludos
Inma