Both of these tools are powerful and can do many of the same things.  You can:

• Run "queries" to extract select information from your data.
• Perform calculations.
• Create reports and forms to add, change, delete, and move around within your data.
• Use Microsoft Word to mail merge or create labels.
• Import information from a different source.

While Excel uses a worksheet to store information, Access uses tables.  To determine which program will meet your need, you have to ask yourself if you can store the information easily on a worksheet or if the information needs to be more dynamic.  For example, lets say I want employee type information but I also know I want to maintain training information, names of dependents, and insurance selection.  It would be more advantageous for you to use Access to maintain this information.  The common link is called a "primary key" which will connect the three separate tables.  In this instance, I would use their SSN or another unique piece of information to "link" them together.  Access uses relational database structure whereas the Excel uses non-relational data structure.