interview questions

I have a set questions which were asked in interview .Could you please provide the suitable answers for the same :

-->what is meant by transaction and if 3^rd sql query failed after first two sql stetements done successfully among 5 statements ;how will you find 3^rd statement only fail

--> what is meant by trigger

--> types and benifts of triggers

--> types of indexes and significance for these

-->define view

--> Define joins and expalin each joins

-->Define stroed procedure and benifits for the same

-->Describe on candiate key

-->Describe on surrogate key