What is "l" (the letter, not the number 1) in Command Line? ... and then my PS1 disappeared!

Question Part 1: I am redoing the Command Line project and am noticing several instances of the “l” command come up in different solution codes and am wondering if … actually I don’t even know what to ask … I just don’t get it … what is “l”? And is its purpose different if it is tagged along with different commands? …

Is the “l” in grep -Rl and wc -l the same?

Question Part 2: So while I was trying to figure out grep -Rl I entered the code below (see first line) … and then I got this really scary warning text (see second line below) … and I noticed that my PS1 environment variable disappeared … and because my PS1 environment variable has disappeared, nothing happens when I try to pull up my ~/.bash_profile (with nano) to go back into the profile to attempt an export PS1 command (see third line below) …

$ grep -Rl Lingua-Franca
grep: warning: recursive search of stdin
nano ~/.bash_profile

This is all quite unsettling and scary as I can’t seem to continue the project because any command that I enter does nothing because there isn’t the PS1 environment variable at the beginning of the line!