What is Vlookup?
Look for a VALUE in the leftmost column of a TABLE and returns a value in the same row from a column you specify. VLOOKUP scans the selected column until it finds the required item (maybe the name of the employee or product or employee code) and then it gives you the required information related to that item (salary of employee, cost of the product, department of the employee).

Why Vlookup?
The simplest answer is to search. There are other advanced uses also like sorting, sample checks in audits etc.

Formula of Vlookup
=Vlookup{lookup_value, table_array, Column_index_number, (range_lookup)}

Lookup_value: Value to look for in the range or table (for example you are looking for Ram or an employee code)

Table_array: Range or Table in which you look for the value (here Ram). While selecting the table range always remember to freeze it by using the F4 key.

Range Lookup: You want an exact match then press here 0 (zero) and if you want an approximate match then press 1.
Suppose you are using vlookup to know Ram's salary amount then it means you are looking for an exact salary number. So here press 0 because you want an exact match.
But in case there is range or slab rates regarding commission percent which depends on sales amounts. Like:
Sales Commission %
0 to 500. 0%
501 to 2000. 10%
In these type of cases, we will use approximate match. Because if sales is 250 or 450 commission percent is zero.

Can Vlookup look for data to the left?
The answer is no. It can only look at data to the right.

When there can be errors in using the Vlookup formula?
Answer:
1. While copying the Vlookup formula without freezing the range.
2. Lookup value does not exist. Say we are looking for Jack's salary but in the table no such name exists.
3. Spacing issues.