Newbie lightroom question

turns out lightroom is taken up to much storage on HD and i just found out lighroom is storing all these imported images inside my pictures folder on my mac. All the files ive imported were coming from an external hard drive which I never touch and never delete. My question is,, if i delete the contents of my pictures folder in my HD of my computer will i effect the files on my external hard drive when i plug it in and run lightoom.

I guess what i want is for those files on my external to not be effected, i just want to free up space on my computer by deleting all that imported data.

anybody.