dedicar vs dedicarse
Dedicar is to devote or dedicate something. Dedicarse a is to do for a living — the question '¿a qué te dedicas?' is everywhere.
dedicar
To devote time, effort or a work to someone or something.
Dedico dos horas al día a estudiar.
I spend two hours a day studying.
Devoting time. Dedicar + time + a.
Le dedicó una canción.
He dedicated a song to her.
A tribute.
Dedica mucho tiempo a su familia.
He devotes a lot of time to his family.
Priority.
dedicarse
To work as, to be occupied with — dedicarse a + noun or infinitive.
¿A qué te dedicas?
What do you do for a living?
The standard question about someone's job. Not '¿qué haces?' alone.
Me dedico a la enseñanza.
I work in education.
Dedicarse a + noun.
Se dedica a vender coches.
He sells cars for a living.
Dedicarse a + infinitive.
Tricky bit
'¿A qué te dedicas?' needs 'a'. Saying '¿qué te dedicas?' is a common mistake. And 'me dedico a' answers it: 'me dedico a la informática'.