Question

alguem me explica there was e there were?

Answer 1

são verbos do passado do verbo to be
você vai usar was quando for os sujeitos: I, She, He e It.
E o were vai usar nos demais sujeitos

Answer 2

There was/were : houve (tinha; no sentido de haver no passado)

Usa-se WAS para os pronomes do singular, são eles: I;he;she; it (exceto o you singular)

Usa-se WERE para os pronomes do plural, são eles: You;we;you;they (tanto para o YOU singular quanto para o plural)