What are the reasons to set behavior in a geodatabase? In other words, how would setting behavior impact on the editor's work?
That is an overly broad question. Are you concerned with domains, subtypes, and schema configurations (allow null values, required fields, default values, split rules, etc.)? Are you considering using relationship classes or topology? Are you looking at taking advantage of special data types, such as Network datasets? Do you want to implement parcel fabrics? Each of these settings can have an impact that can make an editor's life more difficult or easy and much of it depends on your business rules.
I am just trying to understand generally how setting behavior relates to a geodatabase.
Did the topics of setting choices I mentioned mean anything to you? If not pick a couple of those topics to explore in discussions here and also start looking up those terms in the help docs.
What are your business rules for data integrity? What have you been using up to this point (shapefiles I assume) and how has that been working for you? What do you like or not like about the way your data is maintained? You can basically make geodatabases as dumb as shapefiles, or you can invest in their peculiar features to enforce integrity and workflows.
Other topics I could mention include configuring feature datasets (required for topology, feature linked annotation feature classes, and a few other things and helpful for organization, but they have several restrictions for inserting new data that can seriously trip you up if the data does not comply with the spatial reference of the feature dataset).
How much of your data is coming from outside sources? That can have a significant influence on your choices. Anyway, the topic is huge and dependent on your business and your needs as far as the settings you choose to use and those you don't.
This sounds more like you're not willing to do research on your own for a class. Put some effort in -- you'll find that you actually understand things better after trying (even if you're not 100% successful).
Look at the ArcGIS Help. There's a lot of documentation on the benefits of adding geodatabase behaviour, as well as the how-to for doing it.
