Not all of what has been said previously, has been absolutely correct in terms of Tratar and Intentar.
- Probar has a very clear difference and has been elucidated and made distinct very well. Probar is used for testing out, trying food, trying on clothes, for example.
- Tratar is to try to do something, to attempt, have a go at, and also means to treat, as in the manner of behaviour you exhibit to a person.
- Intentar is to intend to, to mean to do something.
It is a subtle difference, but with tratar, to try to do something is to make the attempt (when used in the present tense), whereas with intentar, it is to have the intention of doing it while used in the present tense, and not necessarily be engaged in actively doing it.
Intentar in the present tense is more closely equivalent to tratar in the future tense (although there is a nuance and it is not entirely the same). For example,
"I intend to go to the party" = "I will try to go to the party".
"Intento ir a la fiesta" o "Trataré de ir a la fiesta".
Note Tratar requires the "de" after, Intentar does not.
How people actually use the verbs, however, is not necessarily reflective of their actual meaning.
In simple terms:
- Probar = to test / try out
- Tratar = to try (to do something) / to attempt / to treat (someone in a certain manner)
- Intentar = to have the intent to / to mean to / to be going to be attempting to / to be expecting to be making the effort to do something with uncertainty as to the actual outcome