What does gas lighting actually mean?

[ssd]

I think I'm being gas lighted but I'm not sure if what I think it means actually means.

Can anyone explain or give different scenarios please

I was gaslighted by a 'friend'. She used to tell me that we'd had conversations about things that we hadn't and would look confused and concerned about me when I couldn't remember. I actually genuinely worried that I had early onset dementia at one point. She would send me messages like 'oh by the way, that's fine about what we talked about earlier and yes it's your turn to pay! Yay! 😊' and I had no idea what she was on about.

This went on for months until I suspected she was stealing from me. I saw her wearing my new top and she said I'd given it to her etc. It was completely ridiculous. Eventually caught her doing it to someone else and the penny dropped. She was laughing about something she'd told another school mum and said 'she didn't say that at all but it keeps her on her toes ha ha ha'. She knew straight away she'd fucked up because everything literally fell into place for me. I've never spoken to or acknowledged her since.

Someone not too long ago posted a thread about their rented home - single parent and youngish child. The child found 2 large pieces of chewed chewing gum in the tiny bathroom pedal bin and commented on it.

The child wasn't allowed gum and was convincingly adamant that it hadn't been theirs. Not the parent's. Landlord denied going into the flat but parent was suspicious of some contractors who had come a couple of months previously, i.e. had been able to obtain or keep a key. Potentially someone was gaslighting there (possibly landlord or contractors).

*Park person
*
That's fucking evil. What is wrong with some people