I know people are scared of pensions but it's just a wrapper with some tax treatment attached to it.
It no different really to an ISA or other type of account. Just different rules.
You do need to keep an eye on how the limits and tax parts work, but there's loads of advice available on this.
Once you've put money into "a pension" wrapper, it's up to you how you invest it. You can do this on your own or with advice, via an IFA etc. Or most platforms have default options which are usually tracker funds.
I have my SIPP (self invested pension plan) in YouInvest and I put it mainly into a fund called Vanguard as it is a tracker with low fees. Vanguard have a number of different products, I've chosen the one that I think suits me - no-one else is involved. YI do charge for holding it and for buying (and selling) units, but I only buy when I chuck a lump sum in so the purchase fees work out as a very small %.
I buy an 'accumulating' fund, which means any dividends the underlying shares throw off within the fund, stay in the fund and I don't get cash out of it - I do this to avoid having to make decisions about what to do with that cash, and this means the fund grows by dividends (as well as whatever it grows by in the market, or loses, shares don't always grow of course).
In my ISA I buy dividend paying shares and funds because I quite like having some cash now and then and deciding what else to buy with it, within the ISA (I never take any money out).
With a pension, you get tax relief putting money in - so, you have to have earned income and you pay that into the pension and therefore pay no income tax on that money (and, in some cases, no NI).
You will get taxed when you take the money out if the income is higher than the zero rate tax band in place at the time - but you can take 25% tax free.
You cannot access the funds at all until you are at least 55 (with some very rare exceptions).
If you have no income you can put in up to £2,880pa and the govt will top that up to £3,600 - why would anyone not do that!?
With an ISA, you put taxed money in, doesn't even need to be income, and you can take it out at any time, no tax is payable on what you take out even if you have invested and the amount has increased tenfold (unlikely, but who knows!).