What does serum for the face actually do?

[Paintbox]

I'm using some as part of the protect and perfect range but I can't get to the bottom of what it's really for. Is it just another moisturiser?

I use the ordinary 1% retinol but if you haven't used retinol before or have sensitive skin I would use their 2% retinoid. I've used retinol for quite a while and the 1% is STRONG

Similar question, sorry. I've been using the no 7 protect and perfect moisturising body serum on my neck as it was in a gift pack I got at Christmas. I find that most facial moisturisers give me spots on my neck and jawline but this serum doesn't. Will it be moisturising enough or do I need to carry on trying normal moisturisers on my neck?

Thank you