what is the difference ?
what is the difference between:
taghir dadan
va
taghir kardan
?

Question

Answer

"taghir dadan" is a transitive verb which means it needs a direct object: (chizi ra) taghir dadan
u do sale pish name khanevadegie khod ra taghir dad.
He/she changed his/her last name 2 years ago.

but "taghir kardan" is an intransive verb and doesn't need any objects
u bad az ezdevaj kheili taghir karde ast.
he/she has changed a lot after his/her marriage.

Answer

As Saeede Mrt said, it's the matter of being transitive or intransitive;

tagir dadan: This book changed my life.   meaning: (in ketab zendegi man ra tagir dad)
tagir kardan: My life changed.       meaning: ( zendegey man tagir kard)

Answer

taaghir dadan is transitive and taaghir kardan is intransitive.