Collecting data from users is one of the central problems in the computer world. It's been addressed many different ways, usually through some sort of tool that displays data entry forms on screen, then validates and stores the entries. SharePoint provides two different approaches for gathering data:
Lists collect simple tables of items.
Form libraries collect complex data sets.
How do you know if the data you want to gather is simple or complex? Mostly, this has to do with the relationship between items. Lists are tables containing rows and columns. It's hard to create hierarchical relationships or complex entry forms, so lists are best for items where most columns contain simple values.
Form libraries collect pages of data using InfoPath form templates. InfoPath supports links to databases, complex validation rules, and spell-checking, and stores data in XML format within the form library. Form libraries are more useful when the entries are linked to a database, need to be sent through email, or contain items that include hierarchical relationships.
If you've read this far, you're probably already familiar with the simple Announcements and Contacts lists. You can enter data in those lists by choosing New Item or Edit in Datasheet from the list toolbar. For simple lists, Edit in Datasheet often works best because you can create new items simply by tabbing to the next row. For lists that contain long text fields or other types of data, ...