"ing" help

I am really confused in use of " ing" form.

I know a word add "ing" is doing something at the present. Like walking, talking, joking, lauging, doing, going, paying.

However, i see "ing" form is using as adjective purpose too, Like " he has a good living condition". why is that?

[Tdol]

The -ing form has various uses. When we say 'interesting book', we are using it as an adjective, and the -ing form seems appropriate to me because the book still has that characteristic.