Linux Sed Bug

[王森]

Hi

### tmp.txt ###
address@hidden learn_sed]# cat tmp.txt
hello world
I'am in china
address@hidden learn_sed]#

address@hidden learn_sed]# sed --version
GNU sed version 4.2.1

address@hidden learn_sed]# sed 's/$/ End/' tmp.txt
hello world End
I'am in china End
address@hidden learn_sed]#
address@hidden learn_sed]#
address@hidden learn_sed]# sed "s/\'/ End/" tmp.txt
hello world End
I'am in china End
address@hidden learn_sed]#

### My Question
I want to know the reason.  \' be equal to Line End ??
If possible , tell me why ?   thanks