What is the significance of '*' (star, asterisk) in the file listing results?

If you are just using ls with no arguments, it appears that you are using an alias for ls. To get the same output, I need to use ls -lF. From the ls manpage:

-F, --classify
          append indicator (one of */=>@|) to entries

-l     use a long listing format

The symbols mean the following:

/: directories
@: symbolic links
|: FIFOs
=: sockets
*: executable files

To test if you are using an alias, use alias ls. Mine (which is the Ubuntu default) says:

$ alias ls
alias ls='ls --color=auto'

More information on using aliases can be found here.

Those files are indeed executable. It's because you have (or your .bashrc file has) specified the -F option. Unfortunately the manpage is not very clear on this:

-F, --classify
    append indicator (one of */=>@|) to entries

But as far as I know * is for executables, / for directories, = for sockets, > for doors, @ for symbolic links, | for FIFOs and nothing for regular files.

Also, the colour green is because you have (or your .bashrc file has) specified the --color option.