bash:variable with double quotes

Question

I am a newbie to bash script programming and when I learned the variable expansion I amd puzzled by the variable.
1.when I want to define a variable,I can do as following:

name=foo
name="foo"
name='foo'

what's the difference between themm? 2.when I want to print a variable,I can do as following"

echo $name
echo "$name"
echo "$(name)"

3.I also encounter the part as following:

name=$(date)

what the "()" do,why it can resolve the command?

I googled my question and read some docs,eg ( http://www.serverwatch.com/tutorials/article.php/3898896/Single-vs-Double-Quotes-in-Bash.htm ) but i am still puzzling,can anyone explain it clearly?

Answer 1

name=foo since the value is not present inside quotes, it won't accept the value which has spaces like name=foo bar

name='foo' this won't expand the text present in the value. That is foo $bar would be read as literal foo $bar . It won't expand $b

name="foo" values within the double quotes would be parsed or expanded.