Question

What does the verb ser in Spanish describe?

Answer 1

It means to be/ like how you are (more permanent traits) 
so like 
its is used when stating: 
the hour, day, and date 
place of origin 
occupation 
nationality 
religious or political affiliation 
the material something is made of 
possession 
relationship of one person to another 
certain impersonal expressions 
where an event is taking place 
essential qualities 

yo- soy -i am 
tu- eres -you are 
el/ella/usted- es -he she you(formal) is 
nostoros-somos -we are 
ellos/ellas/ustedes-son -they are 

its very simple, in fact the most simple i have learned in high school. 
you must know the conjugations as i wrote above 
and then just use it accordingly. 

so say you want to write 
i am funny. 
yo "soy" comica. 

he is a doctor. 
el "es" un medico. 

it is 2 o'clock. 
"son" las dos. 

they are american. 
ellos son americanos. 

we are students. 
nostotros somos estudiantes. 

Answer 2

Ser means to be. I hope that helps you out.