What does the verb to be in spanish describes?

In Spanish, you have 2 verbs for "to be"

ser
soy
eres
es
somos 
sois
son

you use "ser" to express
days, hour...
origin
occupation
possession
qualities
what is something made of
where does an event take place 
relationship (who is este hombre?. Este hombre es su padre ( Who is this man ? This man is her father)


Estar
estoy
estas  (accent on the a)
esta    (accent on the a)
estamos 
estais    (accent on the a)
estan    (accent on the a)

You use "estar" when you talk about how something is

You use "ser" when talking about what is something
Ser is more for descriptions, occupations, characteristics, origins, time as I told you before

Estar 
Think about PLACE
P = physical posture or position
L = location  if the location isn't an event (in this case =ser)
      Mi casa esta cerca de
A = action + Present or past participles (estoy escribiendo = I am writing)
C = conditions (physical and mental) (estoy cansado = I am tired)
E = emotions  (I am happy = estoy feliz)

About SER it was DOCTOR (not sure I remember)
D = decription
O = ocupation
C = characteristics
T = time
O =origin
R = relationships

in fact, that what I try to tell you before but I had forgotten these 2 PLACE and DOCTOR . I know there's another one for "estar" but I can't remember.

Anyway, those two are very tricky !!!

hope I helped !!

I’m not very good with spanish but for number 3
ellas también van.
ellas no van también