BTwin are the in-house brand of kids bikes at Decathlon, and they come in a range of prices and specifications.
The Rockrider ST500 24 inch is one of their steel framed entry level mountain bikes, suited for gentle riding on or off road.
The gearing is 18 speed (which can be more confusing than 6 or 7 gears due to needing to use both hands to change gear).
The v-brakes should be plenty good enough for gentle off roading in fair weather, and the bike has front coil suspension to smooth out some of the bumps on the trail.
The front wheel is quick release, to help with transporting and maintenance, and the tyres are designed for gentle off roading.
Given it’s such a cheap MTB, the BTwin Rockrider offers a really good value entry level mountain bike, that should provide plenty of scope for fun during summer riding.