On the Urban Sports Club website I see information about Annual Memberships, what does it mean?

With Urban Sports Club, you have the option to choose an annual membership, which costs less per month but requires a one-year commitment with no cancellation option. Since you're being transferred from OneFit, your membership will remain monthly with the same membership conditions as before.

If you would like an annual membership instead, you can switch to the Urban Sports Club membership structure entirely (leaving the OneFit structure behind), but this means you won't be able to return to the previous OneFit membership terms.