This article from excelvlookuphelp.com answers your question nicely:
A vlookup looks for a value in the leftmost column of a table and then returns a value from the row that the searched for value is found (how far along that row is determined by you).
The 4 parts to a vlookup formula:
SearchFor this is the value that is being searched for. In our dictionary example it would be the word “elucidate”.
WhereToSearch this is the range in which to search and in which the answer lives. In our example, it would be columns A to C.
WhichColumn this is the column in the WhereToSearch range which has the answer in it. In our dictionary example, it would be the third column.
NearOrExact you decide whether the vlookup should search for a close value or an exact value (in our dictionary example we would set this to false as we do want it to search for the exact word “elucidate”).
Structure of the vlookup formula: