Why does ~ symbol is coming when ls command is given

Question

I was working on a desktop server of Ubuntu 12.04 through putty.

When I was giving the ls command in a directory the text file are given along with the same text file followed by a ~ symbol is provided.

Last login: Tue Nov 12 10:34:45 2013 from 10.3.61.19
ncclab@slave13:~$ cd benchmarks/

ncclab@slave13:~/benchmarks$ ls
config_fermi_islip.icnt  gpgpusim.config       RAY
data                     gpgpusim.config~      running benchmarks
DG                       gpuwattch_gtx480.xml  running benchmarks~
MUM                      gpgpu_inst_stats.txt~

Any file of the name gpgpu_inst_stats.txt is not present actually in that folder. Why is this happening. May be question is simple, but I was curious to know the reason behind it

Answer 1

Generally that means either

1. someone opened the file with a text editor and then saved, and the editor made a backup
2. it's a temporary file
3. it's just just a file with a '~' in the name