Ir ("to go") is a challenging verb, not only because it's an irregular verb but also because it's used in many idiomatic expressions. Equally challenging is the verb irse ("to leave"), which is formed by adding a reflexive pronoun to ir. Some people, in fact, consider ir and irse as two different verbs, while others think of them as the same verb with an alternative reflexive form that alters its meaning. Examples of similar verbs are dormir ("to sleep") and dormirse ("to fall asleep"), caer ("to fall") and caerse ("to abruptly fall"), poner ("to put") and ponerse ("to put on"). The meanings of ir ("to go") and irse ("to leave"), however, are especially different, and people often have trouble distinguishing when to use them.
Ir ("to go") does not use a direct object and focuses on the destination, using prepositions such as a, hacia, and hasta ("to") to indicate where the person is going. You can see two examples (one conjugated and one in the infinitive form) here:
¿Quieres ir a la fiesta? | Do you want to go to the party?
Las niñas fueron al concierto temprano | The girls went to the concert early.
On the other hand, irse ("to leave") focuses the action on the starting point, so it uses prepositions such as de or desde ("from") to express the act of leaving. Note the difference in meaning of the examples if we substitute ir for irse:
¿Quieres irte de la fiesta? | You want to leave the party?
Las niñas se fueron del concierto (desde) temprano | The girls left the concert early.
Now, there is a particular expression that uses the verb irse that has nothing to do with what we have discussed here so far. It is a special construction that links irse directly with another verb in the gerund form (-ndo). These types of constructions are called linked verbs, and while they may use an infinitive or a gerund as the second verb, they all link the verbs without any punctuation or conjunction between them. In particular the irse + gerund construction is used to express the start or continuation of a process. Some examples are below. Pay especial attention to how irse remains in the infinitive form but changes its ending (the reflexive pronoun) to match the subject:
Los niños deben irse preparando para el examen
The kids must start preparing for the exam.
Yo no quiero irme enamorando de ti
I don't want to start falling in love with you.
Tú decidiste irte vistiendo mientras me escuchabas
You decided to start dressing up while listening to me.
The verb irse can be used in the infinitive form, like in the examples above, but it can also be conjugated:
Dejamos el pan ahí afuera, y se va... se va poniendo blandengue, blandengue.
We leave the bread there out, and it starts... it starts getting soft, soft.
Caption 51, Cómetelo - Crema de brócoli - Part 5