I believe in reincarnation.
To me, it's all part of the same picture.
We (our soul, spirit, energy) are born into a particular life. When we die, our soul (or whatever) returns and eventually we come back again.
Often we have memories of our previous lives which we remember as children but forget as we become more settled in the new life/more stable.
Ghosts are our soul (or whatever) that haven't 'returned' properly for whatever reason. Perhaps those in denial that they've died or that are clinging on to their old life for whatever reason. Eventually all souls do return which is why ghosts don't stick around forever (see the Ghosts on the Underground for one that stopped being seen in 1972 for example).
The bits I'm not yet clear on are exactly where we return to...and what our purpose here is.
Some believe we are here as part of spiritual development...that our souls come to this place because they are faced with many challenges here and only once we have reached a certain level of spiritual development do we stop coming back.
It also means that people here (their souls) are all at different levels of spiritual maturity.
Some would say that if you want to know what your soul is, that it's the bit of 'you' that observes your inner voice.
So your inner voice is more like your ego...the bit of you that hears it chattering on and which can objectively consider your own inner voice and whether what it's saying is actually right or wrong is your soul.
And I used to be very anti-anything not scientifically proven, an atheist, non-spiritual.
I suppose I'm now agnostic. I believe there is something but not quite anything that any of the organised religions believe. I believe that all religions - both ancient and modern, Eastern and Western are all trying to describe the same thing but have been bastardised to various extents by the humans involved in recording them.
I realise this is very woo, but that's what I believe currently.
I also believe that there are things we haven't scientifically proven yet - only perhaps glimpsed threads via quantum physics and perhaps in the future we will start to understand more.
This has happened in the case of many things that were once scorned and that pre-date science - like meditation. Which is now proven via MRI scans in studies at Harvard to alter the physical structure of the brain but before that was disregarded as 'spiritual nonsense'