The verbs ser and estar in Spanish are the equivalent of the verb to be in English. The verb estar is mainly used to indicate locations, feelings, emotions, and other temporary states, and to form the progressive tense, and the verb ser is used to indicate occupations, nationalities, origin, personality traits, description of characteristics in general, the time (days, dates, years, and the time on the clock), the general weather of a region and relationships (e.g. he's my boyfriend). Overall, while the former talks about temporary states, the latter talks about lasting states (there are exceptions, of course!).
Here's how they are conjugated:
ESTAR: Yo estoy, nosotros estamos, tú estás, ustedes/ellos están, él/ella/eso está.
SER: Yo soy, nosotros somos, tú eres, ustedes/ellos son, él/ella/eso son.
ANSWERS:
1. Aquí están las fotos de mis vacaciones en España. Mira, son muy bonitas.
The verb están indicates location: Aquí (here), and son indicates a description of the photo.
2. Aquí estoy con mi familia en la playa cerca de Barcelona. Esta chica es mi prima, Maribel.
estoy indicates location, es indicates a family tie (a relationship).
3. Marisol es de Argentina y es profesora de japonés en la Universidad de Barcelona.
es indicates nationality and occupation.
4. En esta foto estamos jugando a las cartas en la cabaña porque está lloviendo.
Estamos is used to form the progressive present tense, and está is also used to form the progressive present tense.
5. Normalmente (normally), el clima de España es muy agradable. ¡Es un país fabuloso!
es is indicating the general weather of Spain, while the second es is used to talk about a characteristic of Spain.
