Could someone explain the UK school system to me please?

We don't have kindergarten in the UK. We have nurseries or childminders which usually accept from 9 months old or even younger sometimes! Preschool is, depending on the one you choose, 2+ or 3+. Some nurseries have preschool rooms. Some preschools will be attached to a primary school so it'll be the September before your child is due to start reception. There isn't a "right" option, you decide which is best for your family! Xx

Nurseries are usually private and children can join as babies and can stay until they start school which is the school year they turn 5. They offer longer days and are usually all year round.
Preschool is like nursery but just a diff setting, usually attached to a school, generally shorter hours offered and usually term time only.
Both of these options are for childcare reasons, or socialising - they are not compulsory.
Reception is the first year your child will start school (the school year they turn 5) then they go into year 1, then year 2, year 3 etc.
I personally wouldn’t hold a child back as they can achieve so much in reception and as you mentioned they will then join straight into year 1 and the transition from reception to year 1 is a big one - so to go from nursery/preschool straight to year 1 would be even bigger if they skipped reception.

I can see the comments above have explained nursery and preschool well. I’m pretty sure that when you defer a child (born I think between May and August) they can now go to reception, rather than jumping into year 1, but I could be wrong. If this is an options you’re considering I would research your county.
Not sure how old your little one is, but if you’re considering them going to preschool, check when you need to apply for it, as I know my current county is very different from my old county.
Go and visit as many settings as you can before applying to nursery, pre school or school. You can ask them as many questions as you would like and they can explain the process of application and what the offer.
I’m from a different country as well and my UK born teacher with a 12yr old daughter husband is clueless as well!! so I’ve done a lot of research when my first one was young.

This also depends where you are in the UK too, in Wales most children start school when they turn 3, in my county it’s the day after their 3rd birthday. The class in school is called nursery but it’s not the same as a regular childcare nursery, and they’re in for half days. It isn’t compulsory but I’ve never met anyone who hasn’t started school age 3. Full time starts age 4.

Thank you for the question! I feel more confused than before but at least I can start researching to make sense of it. Same here, I am not english and went to kindergarten from 3 and school from 7 in my country. My parents held me back and it was pretty straight forward. It is vital to learn how to best navigate this system in order to make the best choices for the child.