I receive the following message when trying to import photos: Your disk Lightroom 6.3.0 update to which you are importing images is low on space. Please remove files or empty the trash to make at least 250MB available before proceeding. ??? What does this mean?? I am not using a disk, an have plenty to space on my Mac.
Of course you are using a disk. When you import, you are placing a copy of your photos onto the hard disk in your computer (or an external HD). The meaning of the error message seems very clear. What part of it don't you understand?
The error message means that your destination location (hard drive which is set for the images to be copied) does not have enough space.
Make sure the destination location is set correctly and it has enough space available for the images to be copied.