Meaning of objects being masked by the global environment

Question

When I load my package into the global environment, I get the following message

> library(saber)

Attaching package: ‘saber’

The following objects are ma         


        

Answer 1

The answers above give the low-level causes.

I just thought it would be useful to point out I got that message when I had a project open in RStudio and I loaded the "same" library of that project.

With the explanations above its obvious doing this creates some kind of conflict.