MTB freewheel not moving back wheel after change of tyre
Halfords Apollo 7 speed bike, likely has a freewheel unit screwed onto the hub. For this repair that would be beneficial in its simplicity.

As the rear cogs are turning, while the wheel does not and you can pedal freely, it seems the freewheel has stopped working. It is not cost effective to try and repair this because replacements are so cheap, so you need to replace the freewheel with a similar spec - temporary workarounds exist. You'll want to know that it is seven speed (check) and then the number of teeth on the smallest cog and the largest cog of the freewheel. Maybe something like "11-28" or "14-28" -  you just need to count them or look for a model code yours. Most freewheels you come across now, with the age of your bike, are standardised enough that you can buy any matching spec you come across, touch wood.

Replacing a freewheel instructions are easy to find, or you might be able to find a shop open at the moment... Not guaranteed! There is (naturally)  a very good page on Park Tool's website here.

If it happens to be a freehub design then it's the freehub of the wheel that needs replacing to achieve the same fix, which is a little bit more involved but instructions should be simple to find. The harder aspect would be finding a freehub that matches your existing one, designs vary more, and the way to find it out is by dismantling the wheel some.