Hola otra vez. I'm not sure where in lesson one you're seeing this. I think Rocket Spanish, like several other programs, is built on the assumption that to learn a language, you need to hear it and become used to hearing and saying common words and phrases and build from there. That may be a little frustrating to those of us who like to have explanations right away for what we're hearing, but many language teachers claim that hearing and speaking should be paramount. Anyway, to answer your question, verbs in many languages, including Spanish, change their endings depending on who is doing the action. This is called *conjugating* the verb. English does much less of this than many other languages. We say I *speak* but he *speaks*, but the verb *to speak* doesn't change much except for the third person singular (he/she/it speaks). In Spanish, however, there's much more change:
I speak = hablo
you (familiar) speak = hablas
he/she/it/you (formal) speak(s) = habla etc. etc.
Rocket Spanish covers verb conjugation in several places, I think, starting with lesson 2.5. If you need more help, you might take a look at what the following sites have to say:
I suggest you bookmark these sites, since you may find them helpful in answering many grammar questions that arise. If you find others that are helpful, I suggest you post them on this forum so that other people may benefit as well.
Buena suerte (good luck).