Learn Spanish (Latin America): Voy a jugar básquetbol con mis amigos. - I'm going to play basketball with my friends.

In Spanish, when you want to say you are going to do something, you always need the word a between the form of ir (to go) and the action word (the infinitive, like jugar). Without a, the phrase is grammatically incorrect.

How do we know who is going to play if there is no yo (I) in the sentence?

The verb voy specifically means 'I go' or 'I am going'. Because the verb form already tells us who is doing the action, the pronoun yo is usually dropped in Spanish unless you want to add special emphasis.

Is it okay to say jugar al básquetbol instead of just jugar básquetbol?

Yes! In some regions (especially Spain), people use al before sports. However, in much of Latin America, it is completely normal to skip al and just say jugar básquetbol, similar to how we say it in English.

Why is the word for 'my' written as mis here?

In Spanish, possessive words like 'my' have to match the number of the things you are talking about. Since amigos (friends) is plural, you must use the plural form mis instead of the singular mi.