Copulative conjunctions link two homogeneus elements, which could be independent. They are y, e, ni (and, nor, neither).
The conjunction y adds information to the sentence.
Yo di mi palabra y no voy a ser candidato.
I gave my word and I won't be a candidate.
Solemos comer y después miramos los partidos de fútbol en la televisión.
We usually eat and then we watch the soccer games on TV.
Mi abuela ha perdido la memoria y no se acuerda de nada.
My grandma has lost her memory and she doesn't remember anything.
When the following word starts with an i, we replace the y with the conjunction e to avoid a cacophonous effect. If the following words starts with an "i" but the sounds is "y" as in "hielo" (ice) we use the conjunction y.
Laura es bonita e interesante.
Laura is pretty and interesting.
Llámame e intentamos buscar un hueco para ir a tomar un café y charlar con más tranquilidad.
Call me and we'll try to find some time to go for a coffee and speak with more time .
The conjunction ni adds to the sentence but in a negative way.
Yo no camino a la escuela ni al parque.
I don't walk to school or the park.
Ni me dijo que se ha comprado un coche ni que le despidieron en el trabajo.
He didn't tell me he bought a car or that he was fired at work.