The verb ser (example sentences) (full conjugation) is used to indicate an attribute or an inherent quality that is not likely to change.

El barco es grande. - The boat is large.
El carro es pequeño. - The car is small.
Mi carro es rojo. - My car is red.
Mi hermano es alto. - My brother is tall.
El banano es dulce. - The banana is sweet.
El niño es guapo. - The boy is handsome.
Este río es muy ancho. - This river is very wide.
El bebé es feo. - The baby is ugly.

Ser is used to signify equivalence or identity between two elements

Alberto es doctor. (Alberto = doctor) - Alberto is a doctor.

María es una buena persona. (María = buena persona) - Maria is a good person.

Ser is used to indicate an inherent characteristic or quality

Julio es joven. - Julio is young.

Sergio es guapo. - Sergio is good looking.

Ser is used to indicate origin

Diego es de Perú. - Diego is from Peru.
Este tapete es de México. - This rug is from Mexico.
Ramón es colombiano. - Ramon is Colombian.

Ser is used to express possession

Esa bicicleta es de Gustavo. - That bike is Gustavo's.
Las llaves son de Julio. - Those keys are Julio's.

Ser is used to talk about time

Son las dos. - It's two.
Es la una y media. - It's one thirty.

Ser is used to talk about dates

Hoy es el cuatro de junio. - Today is the fourth of June.
Es jueves. - It's Thursday.

Ser is used to express the material that something is made of.

La chaqueta es de cuero. - The jacket is made of leather.
El suéter es de lana. - The sweater is made of wool.

Ser is used to express the passive voice in the construction ser + past participle + por.

El concursante es entrevistado por el reportero. - The contestant is interviewed by the reporter.
El alfiler es atraído por el magnetismo. - The pin is attracted by magnetism.

Ser is used to express the idea of "taking place" or happening.
La fiesta es el sábado. - The party is on Saturday.
El concierto es dentro de dos semanas. - The concert is in two weeks.

Ser is used in impersonal expressions.
Es necesario ser puntuales. - It's necessary to be punctual.
Es importante recordar los cumpleaños de los amigos. - It is important to remember friend's birthdays.