Okay, so imagine that the Earth is like a big ball, and a long time ago, there were these big pieces of land that were really close to each other. These pieces of land were called plates, and they were like big puzzle pieces that fit together.
One day, these plates started to push against each other really hard, kind of like when you push two magnets together and they resist each other. The plates kept pushing for a really long time, like millions of years.
All this pushing created a big pile of rocks and mountains, kind of like when you make a tower of blocks. This pile of rocks and mountains is called an orogeny, which is just a fancy word for "mountain-building event."
The mountain-building event that happened a long time ago in Europe is called the Variscan orogeny. It made a big mountain range that stretched across Europe, kind of like a big line of bumps.
So basically, the Variscan orogeny was a time when big plates of land were pushing against each other really hard, and that created a big pile of rocks and mountains that we call the Variscan Mountains.