Your standard Select query is great for displaying every record in a result set. There are times, however, that you just want to display aggregate data, such as summations or counts. A typical example might be when you need to total all the hours that have been spent on a particular project.
As with other types of queries, you will start with a Select query. The fields that you specify should also include the fields that you are going to want to display the aggregates of. After you pick the fields, you will turn the query into a Totals query by clicking on the Totals toolbar button

You will now be presented with a new row called the Total row. In the Total row, you will specify each of the fields as a Group By, which tells Access how to group the records.
The other items you can specify are aggregate functions. Aggregate function are how you perform a particular task, such as summing the values. You can perform the following aggregate functions:

Click the exercise link below to get a good feel for creating a Totals query.
Creating Totals - Query