How does vacuum works in postgresql

[Rama Krishnan <raghuldrag@xxxxxxxxx>]

Hi Experts, 

I read this tutorials blog on edb it says vacuum has three phases 

1.ingest phase

2.pruning phase

3.cleaning phase

Apart from this blog, no one has explained about the vacuum working 

I m getting confusion on each can anyone explain me 

https://www.enterprisedb.com/postgres-tutorials/how-does-vacuum-work-postgresql

Thanks& Regards

RK