Quoting is important for string expansion in bash. With these, you can control how the bash parses and expands your strings.
If you want to bash to expand your argument, you can use Weak Quoting:
#!/usr/bin/env bash
world="World"
echo "Hello $world"
#> Hello World
If you don't want to bash to expand your argument, you can use Strong Quoting:
#!/usr/bin/env bash
world="World"
echo 'Hello $world'
#> Hello $world
You can also use escape to prevent expansion:
#!/usr/bin/env bash
world="World"
echo "Hello \$world"
#> Hello $world
For more detailed information other than beginner details, you can continue to read it here.