Questions & Answers about Hudebník hraje.
It is in the nominative singular. That is the basic dictionary form and the form typically used for the subject of the sentence.
So in Hudebník hraje, hudebník is the person doing the action.
Czech normally has no articles. So hudebník can mean:
- a musician
- the musician
The exact meaning depends on context. English must choose, but Czech usually does not.
Hraje is the 3rd person singular present tense of the verb hrát.
Here it can mean:
- plays
- is playing
Czech present tense often covers both the simple present and the present continuous, so context tells you which is meant.