The verb ser (conjugation) means "to be". It is completely irregular in the present tense.
||you guys are
||you all/they are
Ser is used to signify equivalence or identity between two elements:
Mi esposa es doctora. - My wife is a doctor.
Ser is used to indicate an inherent characteristic or quality:
El niño es guapo. - The boy is handsome.
Ser is used to indicate origin:
Yo soy de Colombia. - I'm from Colombia.
Ser is used to express ownership or possession:
Ese carro, el cual está muy sucio, es de Enrique.
That car, that is very dirty, is Enrique's.
Ser is used to express the time of day:
Son las doce. - It's twelve o'clock.
Ser is used to talk about dates
Es el primero de enero. - It is the first of January.
Ser is used as a true auxiliary, when it forms the passive voice.
The verb ser is often confused with the verb estar. Many teachers state the following rule:
Ser denotes a permanent state.
Estar denotes a temporary state.
This rule should not be adopted because it is often incorrect. The following simple rules will enable the student to use the verb ser correctly.
Ser is used:
1. To form the Passive Voice, as:
El cartero trajo las cartas--Active
The postman brought the letters.
La carta fué traída  por el cartero--Passive 
The letter was brought by the postman.
Footnote 1: The Past Part. following "Ser" and "Estar" agrees in gender and number with the subject of these verbs.
Footnote 2: Este cuarto es barrido todos los días (this room is swept every day) is passive voice, because we speak of the action of sweeping, viz., somebody sweeps the room every day. Este cuarto está barrido--no voice; "barrido" is used as an adjective to denote state or condition.
2. To denote an inherent  quality, as:
La nieve es blanca: Snow is white.
El hombre es mortal: Man is mortal.
Footnote 3: Inherence = a fixed state of being in another body. A quality may be inherent "for the time being," as: Juan se ha alistado por dos años, entonces es soldado: John has enlisted for two years, then he is a soldier.
Ser must be used:
1. Before any noun (even if an adjective or article intervenes), as:
I am a merchant.
Es un corredor de cambios bien conocido.
He is a well-known exchange broker.
Son buenos valores.
They are good securities.
2. When "to be" is used to denote possession, as:
Los trapiches son de estos fabricantes.
The sugar mills belong to these makers.
3. When "to be" us used impersonally, as:
Es necesario tomar medidas legales.
It is necessary to take legal proceedings.
4. Before the words "Feliz," "Infeliz," "Pobre," and "Rico." 
Footnote 4: These are not, strictly speaking, "inherent qualities," but they are spoken of as such.