Hello Trixie,
Those are big words and they cover very large concepts. They also mean different things to different people because they are used across a variety of different spiritual traditions and faiths.
However the easiest way to explain it is like this,
Mindfulness = This can refer to – an attitude of being aware of your surroundings and what is happening in the present moment
– being aware of your thoughts and how they effect you
– a type of meditation which encompasses one or all of the above.
Attachment = This generally means being emotionally connected to an object, person a situation or an outcome. In most Buddhist traditions attachments are seen as negative and a hindrance to spiritual progression. This is because when our attachment is challenged, either because a person or object leaves or a situation changes, we experience emotional pain. Attachment is not the same as love, so avoiding attachment should not be seen as avoiding all relationships.
Loving Kindness = This is closely tied to compassion. Loving kindness isn’t like loving in a romantic sense. In an ideal world an attitude of loving kindness doesn’t expect anything in return. Loving Kindness can be used to a type of meditation which is used to generate compassion towards all living beings.
I hope that helps.