the meaning of で in 私は学生で友だちはいしゃです。


Can anyone tell what で means in this sentence: 私は学生で友だちはいしゃです。Thank you. It
looks like the で in this sentence means "and" but I'm not really sure.




You are right, it means "and".

That is the te-form of the copula だ.  
According to "A Dictionary of Basic Japanese Grammar", page 466:  
"The te-form functions, in part, to link sentences"

Examples:  
ジムは日本へ行って、勉強した。  
Jim went to Japan and studied.

このステーキは安くて、美味しい。  
This steak is cheap and delicious.

このアパートは静かでいい。  
This apartment is quiet and good.

父は先生で、英語を教えている。  
My father is a teacher, and teaches English.

