based on your answer,



1-so by telling me to enter duration as 4 days, you are in a way telling me that, the first time I enter duration for an activity, I should first think of it as if it will be done by just one (1) full time resource? such as i should calculate "how long would it take for just one full time resource to finish this", and then i do the math myself outside, and come up with 4 days and enter that?

2-as soon as I assign 4 days, and then enter just one (1) full time resource, the project automatically multiplies 4 days by 8 hours (because lets say we had set a full day to 8 hours) to come up with 32 hours?

You may certainly work by either specifying duration or entering the work for each resource and letting Project calculate duration.

You expressed that you knew how long a task took one person. How long is duration. If you said you knew a painter could paint 100 sq feet of wall in 8 hours of work -- that is work.

Use what ever method makes the most sense for you. You are correct -- if you set duration, Project will calculate work based upon:

Duration * assignment units = Work

You can specify work and Project will recalculate duration based upon:
Work/Assignment units = Work.